bluuebunny/crossref_metadata_2025 huggingface dataset:
Experiments on Arc Perturbation in Turbulent Gas Flow
Authors: Michel G. , Rothhardt L.
Published: July 2007

Electric arcs burning in a strong, turbulent, axial nitrogen gas flow are studied. Time‐resolving (framing) picture series of the arc and its deformations are taken through the quartz tube channel wall. Individual perturbations like kinks exist under strong, turbulent flow conditions. They move with constant acceleration in the direction of the cold gas flow. The temperature of the arc core is disturbed at the position of these disturbances, too. This shows up most distinctly, if the decay of the arc after short‐circuiting is studied, as has been done additionally.
Beat Heating of Collisional and Magnetised Plasma
Authors: Arora B. B. , Phalswal D. R. , Varma N. L.
Published: July 2007

The heating of a plasma by stimulating plasma electrons as well as plasma ions with two anti‐parallel electromagnetic waves under the influence of a uniform static magnetic field is studied using Maxwell's equations and equations of motion. A formula for the power absorption per unit volume of the plasma is derived and effects of collisions and magnitude and orientation of the magnetic field on the beat heating are examined numerically. It is observed that the average power absorption in the absence of ion‐neutral collisions in the plasma barely exceeds unity in the units of pure Langmuir mode excitation where as in the presence of ion‐neutral collisions the power absorption immediately shoots up to a very high value.
The State of the Theory of Vacuum Arc Cathodes
Authors: Hantzsche E.
Published: July 2007

The physics of vacuum arc cathodes, the advances in their interpretation and the still unsolved problems are summarized. Starting from the experimental experiences the theories of stationary arc spots are described, with their assumptions and variants, their successes and deficiencies. It is shown that an extension of these models by inclusion of non‐stationary processes is inevitable. Such processes are suggested and their importance in a theory of the dynamic arc spot is investigated. Finally the role of surfacecontaminations is discussed, and the general applicability of the vacuum arc models to all kinds of arc electrodes is emphasized.
On the Rotational Distribution of N2 in the ArN2‐Discharge. The OO‐Band of the Second Positive System
Authors: Venzke D. , Mizeraczyk J. , Szczepanska H. , Korn E.
Published: July 2007

The rotational distribution of the OO‐band of the second positive system of N2 was determined by the Ornstein method in the glow discharge of an argon‐nitrogen mixture at medium pressure. Evidently, for the rotational R‐ and P‐lines some straight lines can be fitted for rotational quantum numbers between 2 and 60 according to usual representation. The slopes of the curves indicate that the Boltzmann distribution does not exist for all the levels. For each of these straight lines can be declared a value of rotational temperature. The dependence of the several rotational temperatures on the discharge current is essential lower than the corresponding dependence of the gas temperature, which is calculated by means of the energy balance. The influence of the energy transfer from metastable argon atoms to ground‐state nitrogen molecules on the rotational distribution seems to be insignificant. Comparisons with rotational distributions in pure nitrogen plasmas point at the influence of interactions between nitrogen species.
On the Maxwellian Regimes of the Electron Component in the Plasmachemical Reactors of Beam‐Plasma Type
Authors: Mikhailovskii A. B.
Published: July 2007

A problem of description of the electron component in the plasmachemical reactors of beamplasma type is examined. Conditions under which the electrons have a velocity distribution close to the Maxwellian one are elucidated. A hydrodynamic approach for description of the electron component in the Maxwellian regimes has been suggested instead of the kinetic approach developed by Winkler et al. [Beitr. Plasmaphys. 19 (1979) 319]. A method of calculation of the non‐Maxwellian additive to the electron distribution function is formulated, for the proposed hydrodynamic approach to prove. A critical analysis of computer results found by the kinetic approach is given.
On the Theory of Corona Discharge
Authors: Belevtsev A. A. , Biberman L. M.
Published: July 2007

Fundamentals of microscopical theory of the corona discharge are considered. Main mechanisms of generation and disappearance of charged and excited particles are discussed for the example of the helium discharge. An important role of pair ionizing collisions of metastable particles is indicated. Field configurations and distributions of charged and excited particles in the discharge gap are obtained, the corona voltage‐current characteristics are calculated. It is shown that the presence of nonlinear ionization processes may result in hysteresis phenomena. In particular, on set and offset potentials of the corona discharge may differ considerably. Probable features of the corona discharges in some other gases are discussed qualitatively.
Metastable Decomposition of Ar3+ Cluster Ions Into Ar2+ and Ar+
Authors: Stephan K. , Märk T. D. , Märk E. , Stamatovic A. , Djuric N. , Castleman A. W.
Published: July 2007

In this note we present the first account of a study of metastable (unimolecular decay) and collision‐induced dissociation of Ar3+ cluster ions using an experimental setup consisting of a molecular beam‐electron impact ion source and a double focussing (reversed Nier Johnson geometry) mass spectrometer. The existence of the following metastable decay processes (accessible by our sampling time window) could be demonstrated: Ar3+* → Ar2+ and Ar3+* → Ar+. The processes were studied as a function of electron impact energy. The present results are of importance in order to provide some guidance for the development of appropriate theoretical models for the dissociation of cluster ions.
Dc Breakdown of Ultra‐High Vacuum Gaps
Authors: Nevrovsky V. A. , Rakhovsky V. I. , Zhurbenko V. G.
Published: July 2007

A review of mechanisms of the initiation of vacuum breakdown is presented and role of anode surface contaminations in enhancement of prebreakdown currents and initiation of breakdown is emphasized. The experimental investigation of vacuum breakdown and prebreakdown phenomena is described. Experiments presented herein show the desorption of anode contaminations under electron bombardment to be an essential factor of stimulation of electrical breakdowns. Possible influence of desorbed gases on prebreakdown state of electrodes is analysed.
Ponderomotive Force Effects due to a Circularly Polarized Electromagnetic Wave
Authors: Stenflo L. , Tomaradze G. P. , Tsintsadze N. L.
Published: July 2007

The modifications in the time‐averaged plasma particle distribution functions in the presence of a large amplitude electromagnetic wave are studied. It is shown that the ponderomotive force is responsible for tail formation, non‐zero particle currents and heat fluxes. Explicit results, which describe those effects, are derived.
Emission Spectroscopic Investigation of the Decomposition of CCl4 in Plasma Etching Processes
Authors: Tiller H.‐J. , Breitbarth F.‐W. , Pfauch G. , Göbel R.
Published: July 2007

The CCl4 plasma decomposition and the etching of SiO2 and Al by the CCl4 plasma is investigated with the aid of emission intensity Iλ of such species as Cl2, CCl, Cl and CO, which are influenced systematically by the etching process. A time independent electron density (ne ≈ 2 · 108 −1 · 1010 cm−3, dependent on plasma conditions) is measured by microwave diagnostics. The ratio Iλ/ne and Iλ/Ireference' resp. (Ireference = IHelium) is a relative measure of concentrations. The ratio Icl2/Iccl is very sensitive against CCl4‐decomposition and etching processes of SiO2 and Al. Its changes during the etching process of SiO2 and Al in a CCl4 plasma are investigated.
Applicability of the Hydrodynamic Approach to the Electron Component in Plasmachemical Reactors of a Beam Plasma Type
Authors: Popkov N. G.
Published: July 2007

In the present work the question of the possible use of the hydrodynamic approach for describing a plasma beam discharge is investigated. It is shown that the condition νei > (νei + νen) X W/nT is the Maxwelliazation criterion of moderate energy particles in a plasma beam discharge. In this case the value of moderate energy is less than 3÷4 values of plasma electrons thermal ernergy.

The influence of the tail of the distribution function on electron heating is considered qualitatively.
[Russian Text Ignored]
Authors: [Russian Text Ignored] [Russian Text Ignored]
Published: July 2007

A theory of the magneto‐acoustic radiation from an upper‐hybrid soliton moving in an inhomogeneous magnetoactive plasma is presented. The derived expression for the spatial distribution of the radiation field is analysed for a linear and two different parabolic density profiles. The energy flux density connected with the transversal part of the magneto‐acoustic waves is investigated.
Measurement of Specific Heats Ratio of Hydrogen Plasma
Authors: Djurović S. , Pavlov M.
Published: July 2007

Adiabatic expansion of plasma behind the reflected shock front in an electromagnetic shock tube has been verified. Electron densities and temperatures have been measured spectroscopically. Assuming complete local thermal equilibrium, the specific heat ratios of hydrogen plasmas have been determined out of expansion rate per a heavy particle directly from the adiabatic expansion law. Noticeably lower values of the ratio are determined at temperatures where ionization and recombination processes are abundant. The ratios determined in this work are in excellent agreement with theoretical values determined in an earlier work.
Perturbed Arcs in Turbulent Axial Gas Flow. I. Averaged Properties and Power Balance
Authors: Michel G. , Rothhardt L.
Published: July 2007

Electric, caloric, radiation and sounding measurements are reported, which were done with an nitrogen are in strongly turbulent gas coolant flow. On the base of this measurements a power balance is established. It allows for the description of the are by a three‐zone‐model, the zones being 1. conducting are core, 2. thermal sheath containing dissociated nitrogen, 3. relatively cold coolant gas. The hot are core is gliding inside of the thermal sheath. The geometrical disturbances, discussed in a preceding paper, do so, too. The dominating power loss is by axial enthalpy flow out of the channel, carried by the dissociated nitrogen in the thermal sheath.
Experimental Investigations of Discharge Characteristics and Plasma Parameters of a Cylindrical Cathode Discharge in a Magnetic Field. II. Plasma Parameters
Authors: Pavelescu G. , Ghiţâ C. , Bâlâceanu M.
Published: July 2007

The experimental determination of the main plasma parameters (i.e. plasma potential, plasma density, electron temperature, intensity of plasma radiation) in the negative glow of a cylindrical cathode discharge in magnetic field is presented. The influence of electrode configuration, gas pressure, discharge current and magnetic field on plasma parameters and their radial distribution is analysed.
Perturbed Arcs in Turbulent Axial Gas Flow II. Fluctuating Local Properties
Authors: Michel G. , Rothhardt L.
Published: July 2007

As a continuation of the research described in Pt. I, local quantities are studied experimentally by electrostatic wall probing, time resolving shadowgraphy and radial luminosity profile scanning of arcs in turbulent axial gas flow. Turbulency of the gas coolant and thermal sheath properties are discussed as well as the consequencies of the gathered knowledge to theoretical modelling.
Stabilization of Long Electric Arcs by Rotating Magnetic Fields of Different Configurations
Authors: Novikov O. J. , Putko V. F. , Sobolev V. S.
Published: July 2007

The results of the investigation of the direct current electric arc under the influence on it of the rotating magnetic fields of the inductors with a different number of poles pairs are given in the article.

The analysis and the comparison of the arc energetic characteristics and of its movement parameters in the rotating magnetic fields of different configurations were carried out.

The comparison of the experimental data and of the results of the theoretical analysis of the arc movement in the 2‐poles and 4‐poles inductors fields was carried out.

A number of original methods for the application of the researched type of the magnetic effect on the electric discharge in plasma techniques and technology was suggested.
Transport Equations of Plasma in a Curvilinear Magnetic Field
Authors: Mikhailovskii A. B. , Tsypin V. S.
Published: July 2007

The problem of transport equations of a collisional plasma in a curvilinear magnetic field is studied. Two main approaches to this problem are presented: that based on using the Boltzmann kinetic equation and the drift kinetic equation approach. In the frame of the first approach a multimoment transport equation set is found which is more general than the transport equation sets of Braginskii and Grad. The tensor equations of this set are described in an arbitrary curvilinear coordinate system. This allow to use these equations in problems of a plasma confined in toroidal magnetic configurations. Simplification of the multimoment transport equation set in the case of high magnetic field is performed. In the frame of the drift kinetic equation approach, a generalization of the drift transport equations derived earlier by the authors (Zh. Eksp. Teor. Fiz. 83 (1982) 139) is given.
Tomographic Measurements of Plasma Temperature Fields
Authors: Pickalov V. V. , Melnikova T. S.
Published: July 2007

The paper presents a mathematical description of tomographic algorithms for experimental data reduction. In a numerical experiment, problems of selection of optimum parameters of a measuring system to attain a prescribed accuracy of the emission coefficient reconstruction were investigated.
Tomographic Measurements of Temperature Fields in Non‐Stationary Arc Plasma
Authors: Melnikova T. S. , Pickalov V. V.
Published: July 2007

The paper presents results of the use of computational tomography techniques for the processing of experimental data obtained with the help of a plasma tomograph. On the basis of the data acquired, physical processes have been determined taking place in plasma, and the behaviour of some integral characteristics of an electric are discharge in a longitudinal magnetic field has been explained. A possibility to determine optically a certain effective electric field strength of an unsteady state plasma has also been demonstrated.
Ion Extraction of Cl Containing Plasmas — Problems and Possibilities of the Investigations of Plasma Processes
Authors: Tiller H.‐J. , Göbel R. , Führ U.
Published: July 2007

The ion extraction is investigated from Cl2‐, SiCl4‐ and CCl4‐plasmas within a planer‐reactor in dependence on pressure and power density. Furthermore the relative ion formation cross sections of the ions fragments of these gases are measured versus the electron energy within a mass spectrometer tube. It will be concluded the decomposition of these gases from the measured ratios of the extracted currents of single ions in dependence on the plasma parameters. The extracted ion spectra extrapolated to a low degree of decomposition are compared with the ion fragments formed by electron impact within the mass spectrometer tube and thereby the effective electron energy in the plasma sheath nearby the orifice estimated.
Analytical and Numerical Study of the Dispersion Properties of a Beam Plasma System for the Case of Maximal Growth Rates
Authors: Leven R. , Bodrow W.
Published: July 2007

A comparison is made between the analytical approximations for the maximum growth rate γmax and the corresponding values of the frequency and wave number, which are used as initial conditions in nonlinear theories and numerical experiments, and the results of an exact numerical solution of the Landau dispersion equation.
Mikrowellendiagnostik nichtstationärer Ne‐Plasmen mittels unterschiedlich bedämpfter Hohlraumresonatoren
Authors: Gundermann S.
Published: July 2007

In diesem Beitrag wird ein modifiziertes Verfahren der Mikrowellendiagnostik vorgestellt, das den Einfluß der Instabilitäten des Plasmas auf die Meßgenauigkeit stark herabsetzt.
Power Reflection, Transmission and Absorption Coefficients for a Moving Plasma Slab
Authors: Singh Y. P. , Varma N. L.
Published: July 2007

Expressions for power reflection (R), transmission (T) and absorption (A) coefficients for p‐polarized wave for a warm, collisional, magnetized and moving plasma slab (with sharp boundaries and thickness d0) are investigated. The effects of plasma slab velocity (β=v/c), electron density (ωp/ω)2 and plasma temperature (KBT) on reflection (R), transmission (T) and absorption (A) coefficients are discussed numerically. It is observed that for the value β=−0.6, reflection coefficient (R) becomes more than unity, whereas absorption coefficient (A) becomes quite negligible while transmission coefficient (T) shows oscillatory behaviour. The variation with plasma frequency (ωp/ω)2 shows that at lower plasma frequency (ωp/ω)2=0.2 transmission (T) and absorption (A) coefficients are minimum while reflection coefficient (R) is maximum.
Colour Plasma Displays by UV‐Excited Phosphors A Review
Authors: Stern W.
Published: July 2007

Though intense work on the development of a full colour flat TV display panel based on gas discharges has produced considerable progress over the last 10 years no practicable technological solutions have been found [1–2]. Of the different approaches the alternating current (ac) discharge has been proved suitable for the alphanumerical and graphical display technique and the direct current (dc) discharge for colour TV panels. To reach such aims as improved optical efficiency, colour gamut and increased life time as well as simpler manufacturing technology and more effective addressing for reducing costs, long‐term basic research in the field of gas discharges and phosphors and the development of special technologies is necessary [3–8]. The present review is an attempt to give a survey of this situation. In Chap. 1 the trends of development, general problems of colour, display types and TV are dealt with, and in Chap. 2 and 3 the literature on dc and ac‐display panels is reviewed.
Interferometric Method for Electronic Density Measurement in a Plasma Focus Device
Authors: Baltog I. , Ganciu M. , Mihut L. , Zambreanu V. , Zoita V.
Published: July 2007

A Mach‐Zehnder interferometer with pulsed nitrogen laser used for electronic density studies in the plasma focus device is described. The light pulse duration of 2 ns enables interferometric measurements to be made at any instant during the plasma evolution in a 20 kJ (20 kV) device. A numerical method for interferogram processing and computation of the electronic density is presented. Some preliminary plasma studies are discussed.
Exchange‐Correlation Contribution for the Thermodynamic Functions of a Hydrogen Plasma
Authors: Fromhold‐Treu I. , Kraeft W. D. , Rother T. , Stolzmann W.
Published: July 2007

For a hydrogen model the exchange‐correlation energy is calculated at any degree of degeneracy. The numerical data run into the T=O — RPA values, which were evaluated independently.

An equation of state for hydrogen without bound states is compared with HNC‐calculations in the nondegenerate limit. The influence of increasing y=miw/me — values for the agreement with limiting results derived analytically is given in detail.
Investigations of the Current Density in the Cathode Spot of a Vacuum Arc
Authors: Anders S. , Jüttner B. , Pursch H. , Siemroth P.
Published: July 2007

A short review is given on the problem of the current density in the cathode spot of a vacuum arc, theoretical models and experimental results are discussed. A new measuring method is presented which is directly related to the current carrying area of the spot. It leads to current densities of 1012 A/m2 at clean surfaces (comparable with results obtained from crater measurements) and 109−1010 A/m2 with contaminated surfaces.
Solitary Leaking Waves in a Plasma Slab
Authors: Gradov O. M. , Stenflo L.
Published: July 2007

Considering a plasma slab we show that electromagnetic field perturbations, which within linear theory are identified as leaking modes, can appear in the form of solitary waves that propagate along the slab.
Ionization Waves in Glow Discharges with Non‐Uniform Magnetic Fields
Authors: Maruyama T. , Nishiyama T. , Kitamura H. , Itagaki K.
Published: July 2007

The properties of ionization waves self‐excited in glow discharges with a non‐uniform axial magnetic fields are investigated experimentally. The fundamental frequency remains almost constant over the tube for the variable magnetic fields, while the amplitude decreases with increasing the field. The wavelength becomes longer at the cathode side of the magnetic coil and shorter at the anode side with increasing the local magnetic field. The dependence of the wavelength on the magnetic field is explained by the changes of the axial electric field in the non‐uniform magnetic field.
Numerical Study of the Instability in a Maxwellian Beam‐Plasma System. I. Single Wave Regime
Authors: Bodrow W. , Koch B. P. , Leven R.
Published: July 2007

The characteristic features of the instability development in a Maxwellian beam‐plasma system with one previously excited standing wave is investigated numerically. The unconformity of the simulation results with those predicted by the Single Wave Model is analysed in a small‐cold‐beam limit.
Transport and Turbulence Experiments in Three Regimes of a Magnetized Plasma
Authors: Vogels J. M. M. J. , Schram D. C.
Published: July 2007

The occurrence of turbulence and its influence on plasma viscosity have been investigated. A simple model of turbulence has been obtained by the balance of the growth of the combined Rayleigh‐Taylor and Kelvin‐Helmholtz instability with the damping by friction against the neutrals, by kinetic viscosity and by turbulent viscosity itself. In the experiment, a hollow cathode arc, three regimes can be distinguished: a kinetic, a frictional and a turbulent regime. By variations of the discharge parameters around a suitably chosen operating point, transitions between the three regimes are caused. It appears that the longitudinal drift velocity is also influenced by the turbulence. A dispersion relation for the large scale oscillation of the whole arc has been derived and checked experimentally.
Investigation of Thermochemical Zirconium Cathodes in Nitrogen
Authors: Zhukov M. F. , Pustogarov A. V. , Kucherov Ya. R. , Zavid ei V. I.
Published: July 2007

For arcs with zirconium cathodes in nitrogen, experimental results are presented about changes of material and structure of the cathode, temperature fields, current densities, heat flows, electron work function and erosion rate. The cathode heat regime is described theoretically. In the experiments, the arc current was 50–200 A.
Multiple Scattering Contributions to the Electrical Conductivity of Non‐Ideal Plasmas:. II. Three Particle Scattering
Authors: Blümlein J.
Published: July 2007

Three particle effects on the electrical conductivity of hydrogen plasmas are investigated within the Green's function formalism. The transport collision frequency due to e− — H(1s)‐scattering is found to cause a significant lowering of the conductivity isotherms for T ≳ 104 K. This behaviour is similar to that found for caesium plasmas.
Thermosolutal Instability of a Rotating Plasma
Authors: Gupta P. N. , Singh K. V.
Published: July 2007

The thermosolutal instability of a plasma is studied to include the effects of coriolis forces and the finiteness of ion Larmor Radius in the presence of transverse magnetic field. It is observed that the effect of rotation is destabilizing only in a typical case. However, the F. L. R. and stable solute gradient have stabilizing effects on stationary convection irrespective of the presence of coriolis forces.
Boltzmann Equation Analysis of the Electron Gas in CF4 Discharge Plasma
Authors: Mašek K. , Láska L. , D'Agostino R. , Cramarossa F.
Published: July 2007

The electron energy distribution function in CF4 gas discharge was numerically calculated for density reduced electric field E/N = 15 ‐ 300 × 10−17 Vcm2 using the Boltzmann kinetic equation. The momentum transfer and vibrational cross‐sections were derived from available experimental swarm parameters while the cross‐sections for inelastic electron‐molecule collisional processes included were taken from the literature. The two‐term spherical harmonic expansion of the distribution function was used in the calculations.
Elektrische Charakterisierung von Hochfrequenz‐Niederdruck‐Gasentladungen
Authors: Schade K. , Suchaneck G. , Albert M. , Weber J.
Published: July 2007

In recent years there has emerged significant interest in low pressure radio frequency (rf) glow discharges which are used widely particulary in IC fabrication. Various parameters of the rf glow discharge have been found to be useful for its electrical characterization; however, there is no uniformity and agreement.

Extensive experimental investigations on various discharge systems have shown, that the self‐bias on the rf driven electrode, the complex conductivity and the breakdown characteristic are preferable parameters of rf discharges. Advantageously the self‐bias and the complex conductivity should be presented in dependence on the pressure and the applied rf voltage. The discharge current cannot be measured quite accurately due to currents via leaky capacitors and the deviations from a sinusoidal form of the current due to nonlinearities.
Probe Measurements of Wave Fluctuations Excited in Glow Discharges
Authors: Ohe K. , Tsunoda K.
Published: July 2007

Fluctuations of the electric field, the charged particle density; the electron temperature and the plasma potential are simultaneously measured by a probe in the positive column of helium glow discharge at a few torr gas pressure by exciting a small amplitude ionization wave. It is proposed that these values can be determined by analyzing the probe current.
Arc Cathode Processes in the Transition Region between Vacuum Arcs and Gaseous Arcs
Authors: Anders S. , Jüttner B.
Published: July 2007

The cathode processes of electric ares on cleaned Cu cathodes were investigated in the transition region between vacuum and atmospheric pressure (argon). The plasma density in the cathode plane was estimated by probe measurements to be n = r are current, r – distance from the spot). It was observed that several cathode spot parameters have an extremum at p ∼ 104 Pa. The crater diameter has a minimum independently of the cathode temperature. The diffusion constant of the chaotic motion determined by framing photographs was found to have a maximum. Some additional, large displacements occurred at that pressure. The diameter of the bright plasma cloud obtained by open‐shutter photographs showed a maximum, the current per spot was found to decrease from 20 A in vacuum to 10 A at atmospheric pressure. It is thus concluded that the spot with the smallest crater radius and a low current per spot, occurring at ∼ 104 Pa, represents the single spot, whereas the spot at higher pressures, and probably also in vacuum, has a complicated nature where the large craters are formed by a cooperation of single spots.
A Study of Ionization Front Velocity in dc Pulsed Plasmas
Authors: Dengra A. , Hernandez M. A. , Colomer V.
Published: July 2007

The ionization front velocity in a de cylindrical plasma is reported. This parameter has been determined as the ratio between the distance separation of two Langmuir probes, Δz, and the time Δt which is needed for the ionization front to cover the distance Δz.

A theoretical model which allows to obtain the functional relationship of ionization front velocity with the stationary electron density has been developed. A good agreement, both qualitatively and quantitatively, has been obtained.
Instabilities Propagated Along the External Magnetic Field in Magnetized Active Plasmas
Authors: Krstić S. R. , Milić B. S.
Published: July 2007

The conditions for spontaneous onset of instabilities propagated along the external (stationary or quasi‐stationary) magnetic field in cold and magnetized active plasmas are considered in collisionless approximation. Attention is given to non‐resonant cases, i.e. to situations in which the modal frequencies of the wave significantly differ from the frequency of coherent electromagnetic radiation arising due to the active particles. It is shown that instabilities are also possible in these non‐resonant cases and that, under certain specified conditions, they develop only in a very narrow wavelength band. The pertaining amplitude increments are evaluated.
Characterization of the Edge Plasma of the CASTOR‐Tokamak
Authors: Hildebrandt D. , Jüttner B. , Jakubka K. , Stöckel J. , Žáček F. , Groetzschel R.
Published: July 2007

The edge plasma of the CASTOR‐tokamak was investigated by Langmuir and collector probes. Te – values derived from both methods agree satisfactorily and are in the range from 15 eV to 45 eV, depending on the minor radius and the magnitude of the discharge current. However, the collector probe measurements indicate an anisotropic plasma and impurity flow in the edge plasma.
New Results in the Field of a Nonideal Plasma. Experiments and Interpretation
Authors: Iakubov I. T. , Likalter A. A.
Published: July 2007

Experiments on the electronic transport, thermodynamic and optical properties of the dense metal vapors are briefly discussed. Interpretation based on the cluster ions and percolation clusters theory is given.
WHOMoVeS: An optimized broadband sensor network for military vehicle tracking
Authors: Hamdi Mohamed , Boudriga Noureddine , Obaidat Mohammad S.
Published: July 2007

With the advance of sensing technologies and their applications, advanced sensor networks are gaining increasing interest. For certain sensitive applications, heterogeneous sensors can be deployed in the monitored space to ensure scalability, high‐speed communication, and long network lifetime. Hybrid sensor networks have capabilities to combine the use of both resource‐rich and resource‐impoverished sensor nodes. This paper proposes a heterogeneous broadband sensor network architecture for military vehicle tracking. Powerful sensor devices with good bandwidth and energy capabilities are used as a communication backbone while energy sensors are used to track moving targets. Copyright © 2007 John Wiley & Sons, Ltd.
Generation of mice with a conditional Foxp2 null allele
Authors: French Catherine A. , Groszer Matthias , Preece Christopher , Coupe Anne‐Marie , Rajewsky Klaus , Fisher Simon E.
Published: July 2007

Disruptions of the human FOXP2 gene cause problems with articulation of complex speech sounds, accompanied by impairment in many aspects of language ability. The FOXP2/Foxp2 transcription factor is highly similar in humans and mice, and shows a complex conserved expression pattern, with high levels in neuronal subpopulations of the cortex, striatum, thalamus, and cerebellum. In the present study we generated mice in which loxP sites flank exons 12–14 of Foxp2; these exons encode the DNA‐binding motif, a key functional domain. We demonstrate that early global Cre‐mediated recombination yields a null allele, as shown by loss of the loxP‐flanked exons at the RNA level and an absence of Foxp2 protein. Homozygous null mice display severe motor impairment, cerebellar abnormalities and early postnatal lethality, consistent with other Foxp2 mutants. When crossed to transgenic lines expressing Cre protein in a spatially and/or temporally controlled manner, these conditional mice will provide new insights into the contributions of Foxp2 to distinct neural circuits, and allow dissection of roles during development and in the mature brain. genesis 45:440–446, 2007. Published 2007 Wiley‐Liss, Inc.
Induction of immunosuppressive functions of dendritic cells in vivo by CD4+CD25+ regulatory T cells: Role of B7‐H3 expression and antigen presentation
Authors: Mahnke Karsten , Ring Sabine , Johnson Theron S. , Schallenberg Sonja , Schönfeld Kurt , Storn Volker , Bedke Tanja , Enk Alexander H.
Published: July 2007

Suppressive functions of CD4+CD25+ regulatory T cells (Treg) are mainly studied by their interaction with conventional T cells. However, there is evidence that Treg also interact with antigen‐presenting cells (APC), leading to suppression of APC function in in vitro coculture systems. Studying the in vivo distribution of Treg after injection, we found that Treg are located in direct proximity to dendritic cells (DC) and affect their functional maturation status. After contact to Treg, DC up‐regulate the inhibitory B7‐H3 molecule and display reduced numbers of MHC–peptide complexes, leading to impaired T cell stimulatory function. When Treg‐exposed DC were used to immunize animals against antigens, the DC failed to produce a robust immune response as compared to control DC. Thus, these data indicate that Treg are able to inhibit DC activation and produce an inhibitory phenotype of DC. Accordingly, Treg may recruit DC for the amplification of immunosuppression by restraining their maturation in vivo and inducing an immunosuppressive phenotype of DC.
Hsp110 and Grp170, members of the Hsp70 superfamily, bind to scavenger receptor‐A and scavenger receptor expressed by endothelial cells‐I
Authors: Facciponte John G. , Wang Xiang‐Yang , Subjeck John R.
Published: July 2007

Heat shock protein 110 (hsp110) and glucose‐regulated protein (grp170) act as anti‐cancer vaccines when complexed to tumor antigens by heat shock. It has been proposed that receptors on antigen‐presenting cells contribute to HSP‐mediated immune responses. Here, we show that hsp110 binds in a receptor‐mediated manner to RAW264.7 macrophages, as does grp170. This hsp110/grp170 binding is inhibited by scavenger receptor ligands, suggesting a role for scavenger receptors as binding structures. We examined scavenger receptor class A (SR‐A) and scavenger receptor expressed by endothelial cells‐I (SREC‐I). We show that hsp110/grp170 binds to both SR‐A‐ and SREC‐I‐expressing CHO cells in a saturable manner and scavenger receptor ligands inhibit binding. Hsp110 also saturably binds mouse bone marrow‐derived dendritic cells (bmDC) and is inhibited by scavenger receptor ligands. When an hsp110‐rat neu (intracellular domain) heat shock complex vaccine is used to pulse mouse bmDC in vitro, an induction of IFN‐γ secretion is observed by CD8+ T lymphocytes isolated from vaccine‐immunized mice. This immune response is inhibited by the application of scavenger receptor ligands to bmDC. Thus, SR‐A and SREC‐I appear to contribute to the binding of hsp110 and grp170 on APC. Scavenger receptors, in general, contribute to the cross‐presentation of hsp110‐chaperoned protein antigen.
Ultra‐Low Catalyst Loading as a Concept in Economical and Sustainable Modern Chemistry: The Contribution of Ferrocenylpolyphosphane Ligands
Authors: Hierso Jean‐Cyrille , Beaupérin Matthieu , Meunier Philippe
Published: July 2007

The challenge of sustainability in modern chemistry will be met with new technologies and processes provided significant progress is made in several key research areas, such as the expansion of chemistry from renewable feedstock, the design of environmentally benign chemicals and solvents, the minimization of depletive resources, and the development of high‐performance catalysis. In this prospect, ligand chemistry is a pivotal science that links modern‐organic,‐inorganic, ‐organometallic, and ‐coordination chemistry through a vast number of valuable applications, precisely associated to catalysis. We review in this article our recent work on catalysis promoted by original ferrocenyl tetra‐, tri‐, and diphosphane ligands. New concepts, taking advantages of this family of branched multidentate ligands, have led to progress in homogeneous catalysis. The search for catalyst longevity and ultra‐low catalyst loadings (high turnover numbers), on the basis of multidentarity effects and robustness of the ferrocenyl backbone were focused on high‐value palladium‐catalyzed C–C cross‐couplings, such as Heck, Suzuki, and Sonogashira reactions. Low catalyst loading was also explored for C–N cross‐coupling in the allylic amination of achiral substrates. The advantages of this newly born family of ligands in the class of multidentate compounds are discussed in light of the valuable information gathered up to now on their reactivity, structure, and mechanistic behavior.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Recent Progress in Asymmetric Catalysis Using Chiral Carbohydrate‐Based Ligands
Authors: Diéguez Montserrat , Claver Carmen , Pàmies Oscar
Published: July 2007

This review describes the use of the most representative carbohydrate derivative ligands in asymmetric catalysis between 1972 and 2006 (approximately). Particular emphasis is placed on the latest results published in the most active period of this area of research (1998 to January 2007). In the first sections we cover the results obtained using homodonor ligands, such as phosphanes, phosphinites, phosphites and dithioethers. In the next sections, we present the results of using heterodonor ligands, such as P–P′, P–S, P–N and N–S ligands. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Selective Determination of Catechol in the Presence of Hydroquinone at Bare Indium Tin Oxide Electrodes via Peak‐Potential Separation and Redox Cycling by Hydrazine
Authors: Aziz Md. Abdul , Selvaraju Thangavelu , Yang Haesik
Published: July 2007

The electrochemical, selective determination of catechol (CT) in the presence of hydroquinone (HQ) is not readily achieved, because the formal potentials of two phenolic compounds are very close. Here, we have developed a simple electrochemical method for the selective determination of CT by using bare indium tin oxide electrodes and employing CT redox cycling by hydrazine. The cyclic voltammetry of CT and HQ was investigated in Tris buffer (pH 9.0), phosphate buffered saline buffer (pH 7.4), and acetate buffer (pH 4.5). Especially in Tris buffer, the anodic peak potential of CT is much lower than that of HQ, resulting in a large difference between two peak potentials (ca. 0.4 V). The difference allows the selective determination of CT in the presence of excess HQ. The anodic current of CT is amplified using CT redox cycling by hydrazine, which also helps to stabilize CT and HQ in Tris buffer for several hours. The detection limits of CT in Tris buffer containing 0.1 mM HQ are 1 μM and 10 μM in the presence and absence of hydrazine, respectively.
Adaptative Potential of Alkaliphilic Bacteria towards Chloroaromatic Substrates Assessed by a gfp‐tagged 2,4‐D Degradation Plasmid
Authors: Kiesel B. , Müller R. H. , Kleinsteuber R.
Published: July 2007

Chloroaromatics are important anthropogenic pollutants in many environmental systems. Knowledge on the microbial detoxification potential of such compounds in extreme environments is still limited. In pristine environments, horizontal gene transfer is the major mechanism for the adaptation of microbial communities to xenobiotic substrates. However, gene transfer mediated by plasmid conjugation from bacteria living in moderate environments to those thriving in extreme habitats might be limited by different growth requirements of donor and recipient cells. In order to assess the potential of alkaliphilic bacteria from a pristine ecosystem to adapt to chloroaromatic compounds, the host range of the 2,4‐D degradation plasmid pJP4 and the expression of the degradation pathway in alkaliphilic bacteria isolated from soda ponds in the South‐Hungarian Lowlands were investigated. Since most antibiotics are unstable under alkaline conditions, the Green Fluorescent Protein was used as a selective marker for monitoring plasmid transfer. The plasmid pJP4 was tagged by a Tn5::gfp cassette outside the catabolic region. The cassette was inserted into the korB gene without affecting replication, partitioning and transfer functions of pJP4. Escherichia coli was used as a donor of the gfp‐tagged pJP4, as its pH tolerance is higher than that of the natural host Cupriavidus necator JMP134. Additionally, alkaliphilic transconjugants were used as donors in a second mating experiment to enable plasmid transfer at higher pH values. Phylogenetic identification of transconjugants by 16S rRNA gene sequencing revealed that the host range of pJP4 among alkaliphilic bacteria comprises the proteobacterial genera of the β‐subdivision (Ralstonia), the γ‐subdivision (Pseudomonas, Halomonas, Idiomarina and other genera belonging to the Alteromonadales), the α‐subdivision (Devosia) and even the Gram‐positive bacteria of the genus Alkalibacterium (Firmicutes). While the majority of the transconjugants were unable to degrade 2,4‐D to a significant extent, five isolates identified as Halomonas sp. degraded 2,4‐D and 3‐chlorobenzoate in the presence of an additional carbon source but were unable to grow on chloroaromatics as the sole carbon and energy source. Enzyme assays after chemostat cultivation revealed that the degradation of chloroaromatics is limited by the low activity of chloromuconate cycloisomerase. The results indicate that the host range of plasmid pJP4 is broader than the range of bacteria capable to express the 2,4‐D degradation trait and that the Halomonadaceae are potential hosts to establish degradative traits for chloroaromatics in alkaline environments.
Enhancement of the NAD(P)(H) Pool in Escherichia coli for Biotransformation
Authors: Heuser F. , Schroer K. , Lütz S. , Bringer‐Meyer S. , Sahm H.
Published: July 2007

In pyridine nucleotide‐dependent, reductive whole cell biotransformation with resting cells of Escherichia coli, the availability of intracellular NAD(P)(H) is a pivotal point for an efficient and highly productive substrate conversion. The question whether an increase of the intracellular NAD(P)(H) concentration could increase the productivity was discussed controversially in the past. This is the first report on an E. coli strain with an increased NAD(P)(H) pool which was tested in a reductive biotransformation system for an increased productivity. Biotransformation was performed with a strain overexpressing a gene encoding an (R)‐specific alcohol dehydrogenase for the stereospecific, NADPH‐dependent reduction of methyl acetoacetate (MAA) to (R)‐methyl‐3‐hydroxybutanoate (MHB). Cofactor regeneration was implemented via glucose oxidation by coexpression of a gene encoding glucose dehydrogenase. The specific MHB productivity (mmol mg–1 cell dry weight–1h–1) enabled a comparison between the E. coli BL21(DE3) wild‐type and a genetically modified strain. The enhancement of the NAD(P)(H) pool was achieved by genetic manipulation of the NAD(H) biosynthetic pathways. After simultaneous overexpression of the pncB and nadE genes, encoding nicotinic acid phosphoribosyltransferase and NAD synthetase, measurements of the total NAD(P)(H) pool, sizes showed a 7‐fold and 2‐fold increased intracellular concentration of NAD(H) and NADP(H), respectively. However, the implementation of an E. coli strain carrying a genomically integrated pncB gene with an upstream T7 promoter for biotransformation did not result in reproducible increased specific cell productivity.
Intracystic hemorrhage in a mediastinal cystic adenoma causing parathyrotoxic crisis
Authors: Manouras Andreas , Toutouzas Konstantinos G. , Markogiannakis Haridimos , Lagoudianakis Emmanuel , Papadima Artemis , Antonakis Pantelis T. , Kafiri Georgia , Bramis Ioannis
Published: July 2007

Background.

We report a case of intracystic hemorrhage in a mediastinal cystic parathyroid adenoma causing parathyrotoxic crisis.

Methods and Results.

A 30‐year‐old man presented with a large neck mass, dyspnea, and abdominal pain. The patient's serum calcium and parathormone levels were elevated. Radiography showed a right tracheal deviation, ultrasonography identified a thyroid nodular goiter extending to the mediastinum with a large (4.0 cm × 5.6 cm) cystic mass adjacent to the lower left thyroid pole. After IV fluid, pamidronate, and furosemide were administered, the patient underwent total thyroidectomy, and excision of the cyst and a small mass (2 cm × 2 cm) adjacent to the upper right thyroid lobe. Histopathologic examination revealed a double parathyroid adenoma and identified the mediastinal lesion as a cystic adenoma with intracystic hemorrhage.

Conclusions.

Intracystic hemorrhage in a functional mediastinal cystic parathyroid adenoma is an extremely rare cause of parathyrotoxic crisis. Aggressive medical treatment should be immediately instituted, and surgery should be performed as soon as hypercalcemia is controlled. © 2007 Wiley Periodicals, Inc. Head Neck, 2008
Elective paratracheal neck dissection for lateral metastases from papillary carcinoma of the thyroid: Is it indicated?
Authors: Khafif Avi , Ben‐Yosef Rami , Abergel Avrum , Kesler Ada , Landsberg Roee , Fliss Dan M.
Published: July 2007

Background.

Therapeutic paratracheal neck dissection for patients with papillary carcinoma of the thyroid is standard treatment. Its use as an elective procedure is controversial.

Methods.

Thirty‐seven patients with papillary carcinoma of the thyroid and evidence of positive adenopathy at levels II‐V underwent selective neck dissection and elective/therapeutic paratracheal neck dissection. Results of preoperative ultrasonography of the neck were compared with the dissection specimens.

Results.

Morbidity of the surgical procedure was minimal (1 permanent hypocalcemia). All specimens showed metastases from papillary thyroid carcinoma: 100% (37/37) in the jugular chain of lymphatics and 83.7% (31/37) in the paratracheal region. The rate of occult (negative physical examination and ultrasonography) metastases in the paratracheal region in the presence of metastases in the ipsilateral jugular chain was 83.3% (20/24).

Conclusion.

The high rate of occult metastases in the paratracheal region and the low rate of surgical morbidity speak in favor of elective paratracheal neck dissection in patients with metastatic papillary carcinoma of the thyroid. © 2007 Wiley Periodicals, Inc. Head Neck 2008
Dynamic survivin in head and neck cancer: Molecular mechanism and therapeutic potential
Authors: Lippert Burkhard M. , Knauer Shirley K. , Fetz Verena , Mann Wolf , Stauber Roland H.
Published: July 2007

Although disease management of head and neck squamous cell carcinomas (HNSCC) has improved significantly, therapy resistance leading to tumor recurrence still counteracts improvement of long‐term survival. Consequently, identification of molecular markers that signal increased risk of treatment failure or, which can be exploited by targeted therapy, is urgently needed. Survivin is strongly expressed in HNSCC, and its proposed dual role as an apoptosis inhibitor and a mitotic effector positioned survivin in the front line of cancer research. Notably, survivin is detected as a cytoplasmic and as a nuclear protein in HNSCC patients, which stimulated numerous studies to investigate and to speculate on the functional and prognostic significance of its dynamic localization. This review focuses on our current understanding of the molecular mechanisms regulating survivin's intracellular localization and discusses its potential prognostic and therapeutic relevance for head and neck cancer. © 2007 Wiley‐Liss, Inc.