bluuebunny/crossref_metadata_2025 huggingface dataset:
On‐line near infrared monitoring of glycerol‐boosted anaerobic digestion processes: Evaluation of process analytical technologies
Authors: Holm‐Nielsen Jens Bo , Lomborg Carina Juel , Oleskowicz‐Popiel Piotr , Esbensen Kim H.
Published: July 2007

A study of NIR as a tool for process monitoring of thermophilic anaerobic digestion boosted by glycerol has been carried out, aiming at developing simple and robust Process Analytical Technology modalities for on‐line surveillance in full scale biogas plants. Three 5 L laboratory fermenters equipped with on‐line NIR sensor and special sampling stations were used as a basis for chemometric multivariate calibration. NIR characterisation using Transflexive Embedded Near Infra‐Red Sensor (TENIRS) equipment integrated into an external recurrent loop on the fermentation reactors, allows for representative sampling, of the highly heterogeneous fermentation bio slurries. Glycerol is an important by‐product from the increasing European bio‐diesel production. Glycerol addition can boost biogas yields, if not exceeding a limiting 5–7 g L−1 concentration inside the fermenter—further increase can cause strong imbalance in the anaerobic digestion process. A secondary objective was to evaluate the effect of addition of glycerol, in a spiking experiment which introduced increasing organic overloading as monitored by volatile fatty acids (VFA) levels. High correlation between on‐line NIR determinations of glycerol and VFA contents has been documented. Chemometric regression models (PLS) between glycerol and NIR spectra needed no outlier removals and only one PLS‐component was required. Test set validation resulted in excellent measures of prediction performance, precision: r2 = 0.96 and accuracy = 1.04, slope of predicted versus reference fitting. Similar prediction statistics for acetic acid, iso‐butanoic acid and total VFA proves that process NIR spectroscopy is able to quantify all pertinent levels of both volatile fatty acids and glycerol. Biotechnol. Bioeng. 2008;99: 302–313. © 2007 Wiley Periodicals, Inc.
Radial flow hepatocyte bioreactor using stacked microfabricated grooved substrates
Authors: Park Jaesung , Li Yawen , Berthiaume François , Toner Mehmet , Yarmush Martin L. , Tilles Arno W.
Published: July 2007

Bioartificial liver (BAL) devices with fully functioning hepatocytes have the potential to provide temporary hepatic support for patients with liver failure. The goal of this study was to optimize the flow environment for the cultured hepatocytes in a stacked substrate, radial flow bioreactor. Photolithographic techniques were used to microfabricate concentric grooves onto the underlying glass substrates. The microgrooves served to protect the seeded hepatocytes from the high shear stresses caused by the volumetric flow rates necessary for adequate convective oxygen delivery. Finite element analysis was used to analyze the shear stresses and oxygen concentrations in the bioreactor. By employing high volumetric flow rates, sufficient oxygen supply to the hepatocytes was possible without an integrated oxygen permeable membrane. To implement this concept, 18 microgrooved glass substrates, seeded with rat hepatocytes cocultured with 3T3‐J2 fibroblasts, were stacked in the bioreactor, creating a channel height of 100 µm between each substrate. In this bioreactor configuration, liver‐specific functions (i.e., albumin and urea synthesis rates) of the hepatocytes remained stable over 5 days of perfusion, and were significantly increased compared to those in the radial flow bioreactor with stacked substrates without microgrooves. This study suggests that this radial flow bioreactor with stacked microgrooved substrates is scalable and may have potential as a BAL device in the treatment of liver failure. Biotechnol. Bioeng. 2008;99: 455–467. © 2007 Wiley Periodicals, Inc.
Degradation of toluene by a mixed population of archetypal aerobes, microaerophiles, and denitrifiers: Laboratory sand column experiment and multispecies biofilm model formulation
Authors: Kim Hyun‐su , Jaffé Peter R.
Published: July 2007

An experiment was conducted in a saturated sand column with three bacterial strains that have different growth characteristics on toluene, Pseudomonas putida F1 which degrades toluene only under aerobic conditions, Thauera aromatica T1 which degrades toluene only under denitrifying conditions, and Ralstonia pickettii PKO1 has a facultative nature and can perform nitrate‐enhanced biodegradation of toluene under hypoxic conditions (DO <2 mg/L). Steady‐state concentration profiles showed that oxygen and nitrate appeared to be utilized simultaneously, regardless of the dissolved oxygen concentration and the results from fluorescent in‐situ hybridization (FISH) indicated that PKO1 maintained stable cells numbers throughout the column, even when the pore water oxygen concentration was high. Since PKO1's growth rate under aerobic condition is much lower than that of F1, except under hypoxic conditions, these observations were not anticipated. Therefore these observations require a mechanistic explanation that can account for localized low oxygen concentrations under aerobic conditions. To simulate the observed dynamics, a multispecies biofilm model was implemented. This model formulation assumes the formation of a thin biofilm that is composed of the three bacterial strains. The individual strains grow in response to the substrate and electron acceptor flux from bulk fluid into the biofilm. The model was implemented such that internal changes in bacterial composition and substrate concentration can be simulated over time and space. The model simulations from oxic to denitrifying conditions compared well to the experimental profiles of the chemical species and the bacterial strains, indicating the importance of accounting for the biological activity of individual strains in biofilms that span different redox conditions. Biotechnol. Bioeng. 2008;99: 290–301. © 2007 Wiley Periodicals, Inc.
Salt‐induced changes in plasmid DNA transmission through ultrafiltration membranes
Authors: Latulippe David R. , Zydney Andrew L.
Published: July 2007

Recent studies have demonstrated the feasibility of using ultrafiltration for the purification of plasmid DNA, but there is still little understanding of the factors governing DNA transmission. Experimental data were obtained for the transmission of a 3.0 kbp supercoiled plasmid DNA through composite regenerated cellulose ultrafiltration membranes as a function of solution ionic environment in a stirred ultrafiltration cell. The dependence on salt concentration was quite dramatic, with the sieving coefficient increasing by more than 80‐fold as the NaCl concentration increased from 1 to 150 mM at a fixed filtrate flux. At the same total ionic strength, the sieving coefficient in an MgCl2 solution was significantly larger than that evaluated in NaCl. The sieving results are consistent with independent studies showing a reduction in the effective plasmid size due to salt specific shielding of intramolecular electrostatic interactions. DNA transmission was also a strong function of the filtrate flux, with negligible transmission below a critical value of the flux. The predicted values of the critical filtrate flux determined using a modified elongational flow model were in excellent agreement with the experimental data. These results clearly demonstrate that salt‐induced changes in plasmid DNA structure have a significant effect on plasmid DNA transmission through ultrafiltration membranes. Biotechnol. Bioeng. 2008;99: 390–398. © 2007 Wiley Periodicals, Inc.
Protein assembly onto patterned microfabricated devices through enzymatic activation of fusion pro‐tag
Authors: Lewandowski Angela T. , Yi Hyunmin , Luo Xiaolong , Payne Gregory F. , Ghodssi Reza , Rubloff Gary W. , Bentley William E.
Published: July 2007

We report a versatile approach for covalent surface‐assembly of proteins onto selected electrode patterns of pre‐fabricated devices. Our approach is based on electro‐assembly of the aminopolysaccharide chitosan scaffold as a stable thin film onto patterned conductive surfaces of the device, which is followed by covalent assembly of the target protein onto the scaffold surface upon enzymatic activation of the protein's “pro‐tag.” For our demonstration, the model target protein is green fluorescent protein (GFP) genetically fused with a pentatyrosine pro‐tag at its C‐terminus, which assembles onto both two‐dimensional chips and within fully packaged microfluidic devices in situ and under flow. Our surface‐assembly approach enables spatial selectivity and orientational control under mild experimental conditions. We believe that our integrated approach harnessing genetic manipulation, in situ enzymatic activation, and electro‐assembly makes it advantageous for a wide variety of bioMEMS and biosensing applications that require facile “biofunctionalization” of microfabricated devices. Biotechnol. Bioeng. 2008;99: 499–507. © 2007 Wiley Periodicals, Inc.
Differential organization of γ‐aminobutyric acid type A and glycine receptors in the somatic and dendritic compartments of rat abducens motoneurons
Authors: Lorenzo Louis‐Etienne , Russier Michaël , Barbe Annick , Fritschy Jean‐Marc , Bras Hélène
Published: July 2007

Premotor inhibitory neurons responsible for the decrease in the firing discharge during fast or slow eye movements selectively target the cell bodies and the dendrites of abducens motoneurons. γ‐Aminobutyric acid (GABA) and glycine, the main inhibitory synaptic neurotransmitters in the central nervous system, act via glycine and GABAA receptors, assembled from various types of subunits, which determine the kinetics of the currents mediated. Therefore, our hypothesis was that the expression of the inhibitory receptors on the somatic and the dendritic compartments, involved in different functions, may differ. In this study, we compared the subcellular patterns of expression of the main GABAA receptor subunits (GABAARα1, α2, α3, α5), glycine receptors (GlyRα1), and gephyrin in the somatic and dendritic compartments of rat abducens motoneurons, using double or triple immunocytochemical experiments with confocal microscopy. Significant differences exist in the patterns of organization and the synaptic expression of the GlyR and GABAAR subunits in the cell bodies and dendrites of abducens motoneurons. In the somata, only the GABAARα1 subunit was expressed, whereas both GABAARα1 and GABAARα3 were present in the dendrites. The GlyRα1 to GABAARα1 density ratio was reversed in the somatic and dendritic compartments (0.9 vs. 2.3). A quantitative electron microscopy study showed that the modes whereby gephyrin reaches its postsynaptic inhibitory synaptic target differ between the somata and the dendrites. Therefore, our results support the idea that a structure‐function adaptation occurs at the single‐neuron level. J. Comp. Neurol. 504:112–126, 2007. © 2007 Wiley‐Liss, Inc.
Discharge Development in ac Plasma Displays
Authors: Röpcke J. , Zahn R.‐J.
Published: July 2007

The discharge development in ac plasma displays is quantitatively assessed on the basis of comparatively great data quantities under well defined parameter conditions by means of computer controlled equipment. Investigated are ac plasma displays of three different sizes: PAF 58, 90 and PAF 128.

The development of an individual discharge in a stationary pulse sequence is described by analyzing the light emitted by the discharge and by comparing the data obtained with theoretical calculations.

Essential characteristics of the pulsed light emission of an ac plasma display discharge are the build‐up time tA, i.e. the period from cell voltage switch‐on to the discharge maximum, and the characteristic time τ, which is the time constant describing the exponential growth of the discharge in its amplification range.

The theoretical model shows the transition, during discharge build up, from directionization of neon atoms, mainly at low τ values, to ionization essentially via the Penning effect at high τ values. Therefore the effective Townsend ionization coefficient is dependent on τ. The measured time constants of the discharge build up are in good agreement with the calculated values. Adaption between measurement and calculation is achieved by variation of the secondary emission coefficient γ of the cathode.
Plasma‐Screening Effects upon Energy Levels and Electron Scattering from Neutral and Ionized Caesium
Authors: Chin Y. J. , Radtke R. , Zimmermann R.
Published: July 2007

Using interaction potentials screened with the Debye‐Hückel length, the effects of plasma shielding on energy levels and electrons scattering from neutral and ionized caesium are estimated. Both energy levels and atomic scattering cross‐sections are found to be sensitive to the inclusion of screening. Relating to the scattering by the Cs+ ion, a low‐energy resonance near E = 0.3 Ryd is found which arises from the f‐wave phase shift and reflects the individual behaviour of the scattering ion.
Properties of the Tokamak Edge Plasma
Authors: Wolff H.
Published: July 2007

A short review of some features of the edge plasma in limiter tokamaks is given. The limits of the simple 1‐D SOL model and the relation between the core plasma are discussed. MARFE phenomena and detached plasma are closely connected with the particle and energy balance of the SOL. Their occurrence is based on the relation of plasma parameters of the edge plasma to those of the core. Important problems of plasma wall interactions are the detection of the impurity sources and sinks and the study of the impurity transport and shielding. The non‐uniform character of plasma wall interactions and their dependence on the discharge performance still renders difficult any theoretical forecast of impurity distribution and transport and calls for better diagnostics.
On the Temperature Dependence of Plasma Polymerization
Authors: Deutsch H. , Kersten H. , Klagge S. , Rutscher A.
Published: July 2007

A simple model is developed to explain the measured temperature dependence of the growth rate of polymerfilms in a C6H6‐Ne‐glow discharge.

The negative Arrhenius‐behaviour obtained that means a decreasing growth rate with increasing temperature — is determined by an adsorption‐desorption‐equilibrium of the monomer particles on the surface.

From the fitting of the temperature behaviour experimentally obtained by probe measurements some characteristic parameters (activation energy, residence time) were calculated by means of the model.
Nonlinear Effects of a Gaussian Laser Beam on Megagauss Magnetic Field Generation in Laser Produced Plasma
Authors: Prabhakar M. V. H. V. , Srivastava M. P.
Published: July 2007

The generation of megagauss magnetic field due to the time dependent part of the ponderomotive force of a self‐focused Gaussian laser beam indicent on a plasma has been studied. Defocusing of the laser beam becomes possible due to diffraction divergence in the case of a weakly nonlinear medium. The influence of defocusing of a laser beam on magnetic field generation has also been investigated. It is found that the magnitude of the magnetic field due to self focusing of the beam is enhanced and is comparable with the observed values, while there is a reduction in the magnitude of the magnetic field when the beam defocuses due to diffraction divergence in the presence of weak nonlinearity.
Hollow Cathode Effect with Double Axial Electron Injection
Authors: Bratescu G. G. , Ciobotaru D. , Dima G.
Published: July 2007

The paper presents a new type of HCE glow discharge obtained with double plane‐conical cathodes. The two identical cathodes are tronconical and screened with 1 mm2 mailed wire net with a 3.5 mm diameter central washer each. The discharge is obtained between the two cathodes and a ring shaped anode equally distant from both. Optimum intercathodic span is 4 mm, allowing for maximum amplifications at the optimum pressure values for the two gases. Employed helium and argon are spectral pure. At the given distance and depending on voltage and gas pressure, a double axial electron self injection cathode effect is obtained between the electrodes, consisting of very large increase of current and radiations.
Experience with Measuring of the Spectral Line Profile by Means of the Fabry‐Perot Interferometer
Authors: Brablec A. , Kapicka V. , Stastny F.
Published: July 2007

Results of plasma diagnostics by means of the Fabry‐Perot interferometer are very sensitive to a right adjustment, a choice of both the working diaphragm and exposition time, etc. Furthermore, a choice of adequate methods applied to the calculation of plasma parameters from experimental data is very important. As it is very difficult to verify the validity of measured results in this case, a sufficient attention was not given to these problems and at present we find only few really useful information in literature, which would correspond with conterporary level of technique. In this paper there is summarized our experience obtained during many years use of the Fabry‐Perot interferometer in plasma diagnostics.
The Hβ Line Dip Shift
Authors: Djurović S. , Mijatović Z. , Kobilarov R.
Published: July 2007

The Hβ line dip shift was measured and compared with experimental and theoretical results of the other authors. Our results are in a good agreement with the experimental results but in a disagreement or even discrepancy with GRIEM'S theory. Plasmas were produced in the wall stsbilized arc.
Influence of the Basic Process Parameters on the Ion/Atom Arrival Rate Ratio during Magnetron Sputter Deposition of Thin Carbon Films
Authors: Petrov I. , Orlinov V. , Ivanov I. , Kourtev J.
Published: July 2007

The behaviour of the ratio of the argon ion flux and the sputtered atom flux to the substrate with the variation of the basic process parameters was studied in a planar magnetron sputtering system. Finding ways to control this ratio is important with respect to carrying out ion‐assisted thin film growth by magnetron sputtering under well‐defined conditions. Combined deposition rate measurements and plasma probe measurements were carried out in order to determine the ion/atom arrival rate ratio. In addition calculations of the neutral atom flux were performed on the basis of a simple model and the results compared with the measured values. A considerable change in the values of the ion/atom arrival rate ratio with the variation of the argon pressure and the discharge power was found under operating conditions, at which the back diffusion of the sputtered material is pronounced. The distribution of the ion flux over the substrate surface was found to become more homogeneous with the increase of the working pressure or the target‐to‐substrate distance.
Plasma Processes in Activated Thin Film Deposition
Authors: Lunk A. , Schmidt M.
Published: July 2007

This paper deals with plasma aspects in physical and chemical vapour deposition processes. A systematic representation of deposition methods is given and possibilities of plasma diagnostic are summerized. Characteristic parameters of electron kinetics (mean free paths, collision frequencies, energy distribution functions) and rate equations for calculation of particle densities are discussed for a plasma in plasma activated physical vapour deposition device. Theoretical results are compared with measurements (Te, Ne, Ez) in the plasma of a TiNx‐deposition device with hollow cathode arc evaporator. Mechanism of plasma polymerisation is discussed. Results of experimental investigations of the plasma in an Ar‐hexamethyldisiloxane D.C. low pressure glow discharge are presented and compared with results of modelling of this plasma taking into account direct‐, stepwise‐ and Penning‐ionization. The necessivity of knowledge of reactive cross sections for understanding of plasma assisted thin film formation processes is accentuated.
Nonlocal Heat flux in the Scrape‐Off Layer of a High‐Temperature Plasma
Authors: Chodura R.
Published: July 2007

A Fokker‐Planck particle code is used to simulate the energy transport in a magnetized plasma at conditions where the mean free‐path length of heat‐flux‐carrying electrons is comparable with or larger than the electron temperature gradient length. Heat fluxes are calculated for the case of a plasma between two reflecting plates at different temperatures and for the case of one reflecting and one absorbing plate.
Monte Carlo Modelling of Impurities: Comparison with Some Jet and Dite Experiments
Authors: Stangeby P. C. , Farrell C.
Published: July 2007

A two‐dimensional Monte Carlo impurity atom/ion code, LIM, was used to model a number of DITE and JET experiments including (a) the ratio of charge states collected by the Matthews probe in DITE, (b) the net erosion pattern on the 1986 JET limiters, and (c) radial and toroidal CI, CII, CIII cloud shapes in the vicinity of DITE limiters.
Study of an Underexpanded Plasma Jet II. Diagnostics with Microwaves
Authors: Anders A. , Ershov A. P. , Isaev K.
Published: July 2007

The properties of the plasma of an underexpanded jet in air were examined by optical and by probe methods as described in a previous paper (Contrib. Plasma Phys. 27 (1987) 203). The jet was produced by an erosion plasmatron with xenon‐filling operating in a single‐pulse regime. Now, independent measurements of the space‐time development of the electron density by microwave interferometry are described. The results of cut‐off and phase shift measurements are in agreement with those obtained by probe diagnostics.
Effects of Hall Currents and Gyroviscosity on the Instability of a Self‐Gravitating Stratified Plasma
Authors: Mehta Vijay , Bhatia P. K.
Published: July 2007

The instability in a horizontal layer of a partially ionized self gravitating plasma has been studied to include simultaneously the effects of Hall currents, viscosity and finiteness of Larmor radius (FLR). The ambient magnetic field is assumed to be uniform and vertical. Proper solutions have been obtained through the variational methods for a semi‐infinite plasma in which the density has an exponential gradient along the vertical. The dispersion relation obtained has been solved numerically and it is found that the growth rate of unstable perturbations decreases with the effects of viscosity, neutral gas friction and FLR. The influence of effects of viscosity, neutral gas friction and FLR are consequently stabilizing. It is found that the Hall currents have a destabilizing influence as the growth rate is found to increase with this effect.
Analytical Models of Free‐Burning Electric Arcs
Authors: Kozlov P. V. , Engelsht V. S. , Zhajnakov A.
Published: July 2007

Two‐dimensional electric arc model based on the solution of the energy equation by means of variables separation method in curve‐line orthogonal coordinates, associated with electrical arc characteristics, is suggested. Quite accurate solution of MGD‐equations complete system for the arc with radial current spreading out of the top nozzle of the conic electrode is produced. Influence of electrode geometry on arc column characteristics in some particular cases has been analysed.
Langmuir Probe Characterization of a RF Discharge Excited in Ar/C2F3Cl Mixtures during Plasma Deposition Processes
Authors: Špatenka P. , Šícha M.
Published: July 2007

The apparatus for measurements of probe characteristic and its second derivative during plasma assisted thin film deposition is described. To avoid the probe surface contamination an impulse method combined with ion bombardment of the probe surface was used. Experimental evidence of the effectiveness of this method in the discharge fed with Ar/C2F3Cl mixtures is given. Measurements of the second derivative of the probe current have indicated an electron distribution different from the Maxwellian. Negative ions have been found in the discharge, the concentration of which has been estimated to be at most by one order of magnitude higher than the electron density.
Excitation Temperature Measurement of Ar + N2 RF Plasma by Spectroscopic Method
Authors: Joshi N. K. , Thiagarajan T. K. , Rohatgi V. K. , Ashtamoorthy T. S.
Published: July 2007

The mixed gas (Ar + N2) plasma has been generated by a 6 KW, 10.3 MHz radio frequency oscillator. The flame got extinguished if N2 exceeded more than 20% of Ar. The Boltzmann plot using spectral intensities of Ar I and NI lines in the wavelength range 4000–4510 Å have been used to determine the excitation temperature. The results show that excitation equilibrium between two species exist since the temperatures are found to be nearly same for both species.
The Influence of Neutral Particle Sources on the Dynamics of Tokamak Plasmas. II. Particle Dynamics and Induced Electromagnetic Fields
Authors: Bachmann P. , Sünder D. , Tskhakaya D. D.
Published: July 2007

In part I of our paper [1] a kinetic theory of the influence of neutral particle sources on the dynamics of tokamak plasmas has been developed and the general solution of this problem has been given for an arbitrary source function. By the use of these results we calculate in this part II the particle's distribution function for different simple source functions. In the case of recycling perpendicular to the limiter surface we derive analytical expressions for the charge density, the induced electric potential and the anomaleous electron density flux transverse to the magnetic field.
Magnetogravitational Instability of a Thermally Conducting Rotating Plasma through a Porous Medium
Authors: Chhajlani R. K. , Vyas M. K.
Published: July 2007

Magnetogravitational instability of an infinite homogeneous, viscous, thermally conducting, rotating plasma flowing through a porous medium has been studied with the help of relevant linearized perturbation equations, using the method of normal mode analysis. Rotation is taken parallel and perpendicular to the magnetic field for both, the longitudinal and the transverse modes of propagation. The joint influence of the various parameters do not, essentially, change the Jeans' criterion but modifies the same. The adiabatic velocity of sound is being replaced by the isothermal one due to the thermal conductivity. Porosity reduces the effects of both, the magnetic field and the rotation, in the transverse mode of propagation, whereas the rotation is effective only along the magnetic field for an inviscid plasma. The viscosity removes the effect of rotation in the transverse mode of propagation.
Spectral Emissivity of Dense Hydrogen Plasma at Balmer Series Limit
Authors: Ershov‐Pavlov E. A. , Krat'Ko L. E. , Chubrik N. I. , Shimanovitch V. D.
Published: July 2007

Spectral emissivity of hydrogen plasma with a nonideality parameter γ = 0.1 ÷ 0.15 has been measured in the wavelength region of 341 ÷ 513 mm using a 6A‐current stabilized d.c. arc at pressures up to 30 bars as the plasma generator. A comparison of the measured data and the data calculated using the Unsöld and Inglis‐Teller formulas shows no evident discrepancies that might be attributed to the additional influence of plasma microfields on the continuum emissivity of hydrogen at Balmer series limit for the range of electron concentrations and temperatures up to 1018 cm−3 and 14500 K, respectively.
Formation of Clusters in Dense Alkali Plasmas
Authors: Redmer R. , Röpke G.
Published: July 2007

The composition of dense alkali plasmas is calculated accounting for the formation of neutral clusters as well as positively and negatively charged molecular ions. The resulting values for the critical point of the liquid‐gas phase transition are in better agreement with experimental data as previous theoretical work. The simultaneous occurence of the metal‐nonmetal transition is discussed by means of the elctrical conductivity.
OCP Dynamical Structure Factor and the Plasma Dispersion: Method of Moments
Authors: Adamjan S. V. , Meyer T. , Tkachenko I. M.
Published: July 2007

The molecular dynamics data of HANSEN, MCDONALD and POLLOCK [1] on the dynamical properties of the classical one‐component plasma (OCP) are compared with the results based on an approximation formula for the dielectric function [2] satisfying all known sum rules and exact relations using HNC plasma static properties [3].
Transport Coefficients for Nonideal Hydrogen and Cesium Plasmas
Authors: Reinholz H. , Redmer R. , Tamme D.
Published: July 2007

The transport coefficients of a nonideal plasma are expressed by equilibrium correlation functions within the ZUBAREV approach. Besides the treatment of the different interactions in a partially ionized plasma, this approach allows also for the currents of the heavy particles ions and atoms. Furthermore, the influence of an arbitrary mass ratio on the transport coefficients is investigated. Explicit results are shown for H (n= 1017… 1020cm−3,T= (1…3) · 104K) and Cs plasma (n= 1015…1021cm−3,T= (3…10) · 103K).
Dynamical Screening and the dc Conductivity in a Fully Ionized Plasma
Authors: Morales F. , Kilimann M. K. , Redmer R. , Schlanges M. , Bialas F.
Published: July 2007

A kinetic equation with a composed collision term (Boltzmann + Lenard‐Balescu‐Landau) is solved numerically. Dynamical screening is taken into account in the e‐e‐scattering. The conductivity of a fully ionized H‐plasma was calculated. In comparison to static screening dynamical screening tends to lower the conductivity.
Determination of the Electrical Conductivity of a Plasma on the Basis of the Coulomb cut‐off Potential Model
Authors: Mihajlov A. A. , Djordjević D. , Popović M. M. , Meyer T. , Luft M. , Kraeft W. D.
Published: July 2007

On the basis of the Coulomb cut‐off potential model [2, 3] electrical conductivity calculations for a H‐Plasma are carried out in a temperature and density range 8000 K ⩽ T ⩽ 50000 K and 1018 cm−3 ⩽ ne ⩽ 1024 cm−3. The electron‐ion scattering is included by the semiclassical result given in [2, 3], whereas the influence of the electron‐electron scattering is included by the well known Spitzer‐factor. The electron‐neutral interaction is modelled by a polarization potential [8] in Born‐approximation. The results for the electron‐ion interaction show a dependence only on the parameter Γc = e2kBT/γrc, whereas the electron‐neutral interaction has a more complicated temperature dependence.
Determination of Parameters of the Arc Plasma of Electrodynamic Macro‐Particle Accelerator by the Method of Simulation of Surface Energy Losses
Authors: Djuric Z. , Mihajlov A. A.
Published: July 2007

In the paper we have presented the model method of calculating electrical arc parameters in the macroparticles' electrodynamic accelerator at the given rail width and the given width between them. The method is based on energy losses simulation at the arc's boundary surfaces and is a modification of the one‐dimensional version of Powell and Batteh's method. It has been shown that the proposed method is adequate for operative use and that it enables the determination of both macroscopic arc parameters · acceleration, length, electroconductivity, mean temperature and density of particles etc., as well as local arc plasma parameters. The values of these parameters are determined by numerical solutions of the self‐consistent system of mangetic‐hydro‐dynamic, material and thermodynamic equations, at the arc's given mass and muzzle voltage between rails. It has also been shown that the proposed method allows the comparison of one‐, two‐ and three‐dimensional arc approximations. In the present paper we have used the method assuming that arc plasma is at most doubly ionized and produced exclusively by copper atoms.
1‐D 1‐Fluid Sol Modeling with Finite Elements
Authors: Zanino R. , Schneider W.
Published: July 2007

We present here the numerical solution of a 1‐D (along the magnetic field) 1‐Fluid time dependent set of SOL model equations (particle, momentum and energy balances) by means of finite element (FE) discretization of the space coordinate. The results are compared with those of the SOLID finite difference (FD) code [W. Schneider, et al., J. Nucl. Mater. 121, 178 (1984)] and good agreement is found between the two. This shows the potential of the FE to work also in the presence of strong convection, as is the case near the divertor plate or limiter ‐ a feature which if confirmed in the 2‐D case will make them particularly attractive for SOL simulation.
Theory of the Ergodic Divertor
Authors: Samain A. , Blenski T. , Ghendrih Ph. , Grosman A.
Published: July 2007

We consider the basic possibility offered by ergodic divertors, which is to establish a high density, low temperature plasma shell diffusely connected tothe wall.
The Application of Langmuir Probes to the Measurements in Flowing Afterglow Plasma
Authors: Sicha M. , Sun Zu Cham , Glosik J. , Tichy M.
Published: July 2007

Langmuir probe measurements in argon flowing afterglow are presented together with probe data analyses. The charged particles density is evaluated from the electron probe current at the space potential and from the saturated positive ion current. The latter is analysed using the method by Zakrzewski and Kopiczynski [15, 16] and both results are compared against each other. A satisfactory agreement almost within the estimated experimental error range suggests that the method [15, 16] brings a reasonable description of a positive ion collection by a Langmuir probe.
Dispersion Relations for Drift‐Alfvén and Drift‐Acoustic Waves in Arbitrary Directions
Authors: Venema M. , Suchy K.
Published: July 2007

A dispersion equation for low‐frequency waves in a fully ionized plasma with slowly varying density and magnetic field is derived from the two‐fluid equations. The solutions are discussed in several limiting cases. Phase‐velocity and refractive index surfaces are presented for the fast and slow magneto‐acoustic waves and for the shear‐Alfvén wave, influenced by the inhomogeneity drifts.
KInetic Description of the Positive Column for Medium Knudsen‐Numbers
Authors: Wallschläger H.
Published: July 2007

We analyze the influence of collisions on a plasma column with cylindrical symmetry in the pressure regime between the collision‐dominated and the free‐fall case. A model is investigated which can handle arbitrary contributions from ion‐neutral‐collisions. One finds an analytic solution for the ion‐distribution‐function which depends functionally on the potential. This electrical potential is calculated numerically — with consideration of the space‐charge‐layer near the wall — and selfconsistently from the Poisson‐equation. From the calculation of the ion‐distribution‐function, of density, flux and temperature of the ions as well as of the potential variation, we discuss the influence of the model parameters. The results are compared with corresponding hydrodynamic calculations.
Theory of a Two‐Gas Gas‐Puff Z Pinch
Authors: Yu M. Y. , Xu Xue‐Ji
Published: July 2007

A simple snow‐plow model for the two‐gas gas‐puff Z pinch is investigated. An expression for the plasma velocity in the central test‐gas region is derived and the radius of maximum compression determined.
Linear and Nonlinear Magnetic Electron Drift Waves in a Nonuniform Strong Magnetic Field
Authors: Stenflo L. , Shukla P. K. , Murtaza G. , Yu M. Y.
Published: July 2007

Linear and nonlinear propagation of magnetic electron drift vortex waves in a nonuniform magnetic field is investigated by means of a generalized adiabatic law which takes into account the effect of strong fields and reduces in the appropriate limits to several well known energy conservation equations in a collisionless plasma. In the linear limit, an instability is shown to exist, whereas in the nonlinear regime, steady‐state dipole vortices associated with the electron drift vortex waves may appear. The anomalous electron energy transport associated with the unstable magnetic electron drift vortex waves is investigated by means of a quasilinear theory.
Coupling Coefficients for Ion‐Cyclotron Alfvén Waves
Authors: Brodin G. , Stenflo L.
Published: July 2007

Magnetohydrodynamic equations for plasmas with large Larmor radii are used to derive the wave coupling coefficients. The results generalize those of previous works.
Nonlinear Pulse Propagation in Unmagnetized Plasmas
Authors: Bhakta J. C.
Published: July 2007

Evolution of pulses for unmagnetized plasmas have been considered. By using Rayleigh‐Ritz optimization method based on trial functions ordinary differential equations for the pulse parameters have been derived. It is found that the character of the pulse parameters depends on the initial wavenumber chirp.
A Group Theoretic Approach to the Magnetohydrodynamic Equations and Group Invariant Solutions
Authors: Ludu A. , Iovitu‐Popescu I.
Published: July 2007

The application of transformation group methods to a system of nonlinear partial differential equations, representing an incompressible M H D plasma, is shown. The structure of the symmetry group is investigated and a theorem of existence of the solutions of the system of equations is given. Some illustrative analytical invariant solutions and their differential invariants will be presented.
Nonlinear Wavepackets in Kelvin‐Helmholtz Instability in Hydromagnetics
Authors: Deysikder S. , Das K. P.
Published: July 2007

The instability of small but finite amplitude waves propagating at the interface of two layers of highly conducting incompressible fluids in relative motion in presence of external uniform magnetic field is studied. Using the method of multiple scales nonlinear evolution equations are derived for both linearly stable and marginally stable cases. It is found that in the linearly stable case both the modes are modulationally unstable. The nonlinear cut‐off wavenumbers are determined.
Spark Temperature Enhancement by Adding a Parallel Capacitor in High Voltage Circuit
Authors: Pavlov M. , Djurović S. , Kobilarov R. , Vujičić B.
Published: July 2007

Temperature of sparks produced by automotive ignition systems have been measured spectro‐scopically. It is shown that by adding a capacitor of the order of 10 to 100 pF, temperature of the arc phase of a spark can be considerably increased.
A Simple Model of Diffuse Vacuum arc Plasmas
Authors: Hantzsche E.
Published: July 2007

The diffuse expanding plasma of low‐current vacuum arcs is composed of and characterized by an almost thermal electron gas and an ion beam with high kinetic energy. It is described theoretically with a two‐fluid hydrodynamic model. By application of thorough simplifications (such as isothermal conditions, constant composition, one‐dimensional treatment) an analytical solution is found in the form of asymptotic power series of the plasma parameters. This solution is used to analyse the plasma ion acceleration, resulting in the statement that the three forces acting on ions (i.e. the electric field, the ion pressure gradient, the electron‐ion friction) are of comparable importance, contributing to the total ion energy roughly 20%, 35%, and 45%, respectively (in case of Cu vapour arcs). As to the electric field and Ohm's law the solution reveals that the potential is falling towards the anode and that the diffusion current exceeds the opposite conduction current with the consequence of a negative resistance of the arc plasma. Finally, the approximations of the solution, limitations of the validity and possible extensions of the model are shortly discussed.
Radiation Efficiency and Kinetic Calculations for the Positive Column in Hg/Ar Mixtures. I. Thg Variation
Authors: Kreher J. , Bartolomäs G. , Wilhelm J. , Stern W.
Published: July 2007

Properties of the positive column of low pressure Hg/Ar discharge have been investigated from the point of view of its application in fluorescent lamps. The results obtained are based on experimental methods to determine both UV resonance radiation fluxes of the 63 P1 and 61P1 Hg levels and to measure the electron distribution function by probes; in addition a kinetic model is applied for the theoretical interpretation of the experimental results and to give a deeper insight into the particle and energy budget. In the present first part of the paper the effects of recently determined τeff‐values on radiation, net collision rates, power transfer and the electron energy distribution for extended parameter values are investigated especially in dependence on mercury partial pressure.
Plasma Diagnostics in a Hollow Cathode arc Evaporation System During TinX‐Deposition
Authors: Lunk A. , Basner R.
Published: July 2007

During the deposition of hard titaniumnitrid films the plasma conditions were investigated with a movable Langmuir‐probe in axial and radial directions systematically. The deposition took place in a hollow cathode arc evaporation equipment (HCAE). We measured the electron energy distribution function (EEDF) or electron temperature, the plasma potential, the concentration of the ions and electrons, the density of the neutral particles and the evaporation characteristics. A twodimensional model was developed to describe the plasma under the conditions of the plasma activated vapour deposition (PAPVD). The model uses the first and second momentums of the Boltzmann equation (hydrodynamical description). Under experimentally realized geometrical conditions the electron temperatures are calculated by this model and are compared with experimental results.

The measured second derivative of the probe characteristic (measured by the sample and hold method) showed, that the EEDF is a Maxwellian one. The measured electron temperatures are in the range of 2.5–4 eV in accordance with calculated values.
Nonsymmetrical Electromagnetic Waves in Partially Plasma — Filled Waveguide
Authors: Ivanov S. T. , Alexov E. G. , Malinov P. N.
Published: July 2007

The dispersion of nonsymmetrical electromagnetic waves in waveguide, partially filled with plasma, is studied numerically and experimentally. An external d.c. coaxial magnetic field is applied to the waveguide. The dispersion equation of these waves is obtained, and it is solved numerically for the experimental conditions. Results are obtained, which show coupling of the waveguide HEl1‐modes with the family of the high‐frequency plasma HEln‐modes. The numerical dispersion curves are experimentally examined, and the influence of the magnetic field and the plasma density is studied.
Electromagnetic Waves in Waveguide Partially Filled with Semiconductor Plasma
Authors: Ivanov S. T. , Alexov E. G.
Published: July 2007

The dispersion of electromagnetic waves in waveguides partially filled with semiconductor plasma is investigated for unmagnetized and for strongly magnetized plasma.

The effects which may be useful for the plasma electronics are found: In such waveguides there exist a large number of slow waves with typical frequencies ω ≈ ωP/√ϵL. The filling at which the different modes at fixed phase velocity are maximum separated in wavelength is found. The thickness of the semiconductor layer at which this effect arises is about hundred micrometers and depends on the crystals' type. In addition to this, in strongly magnetized semiconductor plasma the maximum frequency separation of the typical plasma waves is found at fixed filling.

Is it shown that in such systems there exist many surface waves which are of the slow wave type.

In the case of strongly magnetized plasma coupling between nonsymmetrical EH‐ and HE‐ modes is shown to exist.
Negative Ions, Ozone, and Metastable Components in dc Oxygen Glow Discharge
Authors: Khvorostovskaya L. E. , Yankovsky V. A.
Published: July 2007

In a dc glow discharge in oxygen, the concentrations of minor components of O2(a1Δg), O2(b1 Σg), O3, O(1D), as well as nagative ions and electrons have been measured. Balance equations have been derived which describe satisfactorily the stationary concentrations of these components as functions of gas pressure and discharge current. For the first time, the rate constants of important aeronomical reactions (a) O− + O2(a1Δg) → O3 + e, (b) O2− + O2(a1Δg) → 2O2 + e and (c) e + O3 → O2− +O have been measured as functions of gas temperature T and mean energies of ions Ei and electron E6: Ka = (2.5 ± 0.5) · 10−9 · (T/300)4 ± 0.4· (Ei/0.04)−2.6 ± 0.4 cm3/s for T = 385−605 K and Ei = 0.10 − 0.66 eV; Kb = (1.0 ± 0.3) · 10−10 · (T/300)−2 ± 0.5 · (Ei/0.04)0.23 ± 0.05 cm3/s for T = 330−605 K and Ei = 0.09 + 1.5 eV; Kc for Ee = 0.8÷5 eV.
Barrier Discharge The Transferred Charge and Ozone Synthesis
Authors: Gibalov V. I. , Dřímal J. , Wronski M. , Samoilovich V. G.
Published: July 2007

We have undertaken an experimental investigation of the influence of the conditions of barrier discharge implementation such as: the discharge gap value, the type of gas, and the polarity and dielectric permittivity of the dielectric electrode on the value of charge transferred in a micro‐discharge. It is shown that the increase in the specific capacitance of the electrodes leads to proportional increase in the transferred charge value, reaching 100–200 nC in a discharge gap 1 mm, in air. In this case the amplitude and duration of a current pulse in the microdischarge reach, respectively, 10 to 15 A and 40 ns. It is also demonstrated that in air with increase in the discharge gap value one can observe a decrease in the efficiency of the ozone synthesis whereas in oxygen there exists a more complicated dependence: the maximum of efficiency is observed at a discharge gap value of 0.7 to 1.0 mm.
A Simple Theoretical Analysis of a Discharge Pumped XeCl‐Laser
Authors: Krause U. , Kleinschmidt J.
Published: July 2007

A simple theoretical analysis of the discharge characteristics and the laser output performance of a discharge ‐ pumped XeCl‐laser is described. Validity of the model is confirmed by comparing the results with the measured time histories of the discharge voltage and current as well as with measured laser‐output‐energies. The model allows qualitative explanations with respect to the laser output energy in dependence on the total gas pressure, the concentrations of Xe and He as well as the load voltage of the power supply and the primary stored energy.
Two‐Fluid Theory of Presheath and Space Charge Sheath in Low Pressure Plasmas
Authors: Valentini H. ‐B.
Published: July 2007

In low pressure plasmas the transition between the presheath and the sheath is investigated taking into account solutions of a two‐fluid model in the whole plasma. The kinetic theory is reviewed only shortly. The hydrodynamic theory is described in detail. In addition, new results are given. Boundary conditions necessary for the hydrodynamic description are derived from the electron kinetics.

The two‐fluid equations supplemented by the Poisson equation constitute a set of nonlinear differential equations with isolated singular points. In addition, this is a singularly perturbated problem if the space charge sheath is thin. Singular points occur if the ions or the electrons attain the corresponding sound speed. The mathematical problem can be split into a boundary value problem for subsonic ion velocities and in an initial value problem for the hypersonic range.

Solutions are obtained by combination of analytical and numerical methods. The numerical integration involvesinstabilities in the subsonic range if simultaneously the plasma is collision dominated and the space charge density is very small in the interior. Several methods are given to reduce or to avoid these difficulties. It is shown that a magnetic field, directed parallel to the tube wall, can reduce the voltage drop across the sheath substantially. In a positive column the radial variation of the electron temperature is calculated by means of the two‐fluid model. Sheath criteria are discussed.
Trends in the Plasma Activated Deposition of Hard Coatings
Authors: Lunk A.
Published: July 2007

Plasma assisted deposition of hard coatings is a well‐known technique to improve the properties of bulk materials. From a detailed knowledge of the wear mechanisms and the characteristic properties of the coated materials there can be deduced the requirements to the deposition technique. These requirements are discussed in relation to the plasma parameters and the plasma ‐ surface interaction for the plasma assisted physical vapour deposition and the plasma assisted chemical vapour deposition.