bluuebunny/crossref_metadata_2025 huggingface dataset:
Spektrallinienprofile des neutralen Argons im nahen infraroten Spektralbereich
Authors: Musielok J.
Published: July 2007

In dieser Arbeit wurden Untersuchungen der Linienprofile von ArI im nahen infraroten Bereich durchgeführt. Die Strahlung der Plasmasäule wurde auf Photoplatten mit Hilfe des Plangitterspektrographen PGS2 registriert. Für ausgewählte Linien wurde die spektrale Intensitätsverteilung gemessen. Aus der gemessenen Halbwertsbreite und dem Emissionskoeffizienten der Hβ‐Linie wurden die Elektronenkonzentration und die Temperatur bestimmt. Mit diesen Plasmaparametern wurden die theoretischen Profile der ausgewählten Linien berechnet und mit den experimentellen Ergebnissen verglichen. Es wurde eine gute Übereinstimmung zwischen Experiment und Theorie festgestellt.
Cathode Phenomena with Arcs and Breakdowns in Vacuum
Authors: Jüttner B.
Published: July 2007

A short review is given on cathode phenomena in vacuum. Based on experimental results about temporal and spatial development of craters, arc spots and breakdown flares, conclusions are drawn with respect to the dynamics of crater heating, the connection of craters with spots, the current density, the reason of arc spot movement, the nature of different spot types, and the analogy of cathode flares with arc cathode spots. Referring only to surface processes, some general results could be obtained which allow a unified description of various cathode phenomena.
On the Motion of Unipolar Arcs in a Tokamak
Authors: Hintze W. , Laux M.
Published: July 2007

Tracks of unipolar arcs found on parts of the T‐10 tokamak (shield and pipe section of the surface analysis station WASA, edge of the movable limiter) are analyzed.

It is the aim of this paper to explain the observed deviations of the arc motion from the first order retrograde direction. It is shown that the drift of the arc which occurs if the magnetic field is inclined to the cathode surface, and which was studied in detail by Robson [1], causes the deviations. To this end, arc tracks on three differently shaped electrodes (cone, cylinder, sphere) are calculated theoretically and compared with the data from T‐10. Good agreement is obtained if the drift angle is approximately equal to one half of the inclination angle of the magnetic field. The present investigation is consistent with the model of retrograde arc motion of Robson and von Engel [2, 3].
[Russian Text Ignored.]
Authors: [Russian Text Ignored.] B. , [Russian Text Ignored.] M. H.
Published: July 2007

An investigation of the heterogeneous low temperature plasma ionization is stimulated by practical needs. Earlier theoretical studies of the ionization process are connected with many difficulties and realized by simple models.

In this paper a solution of the kinetic equations of the electron‐ion process and the Poisson equation for a self‐consistent electrostatic potential is presented.

A pecularity of the volume density determination of the electron‐ion atmosphere around a solid particle, the connection between the integral and local density of charged particles and the own particle volume are taken into consideration.

The influence of characteristic parameters of the condensed phase on the equilibrium electron density is received.
Stability of a Stratified Partially Ionized Plasma in a Horizontal Magnetic Field
Authors: Sankhla V. D. , Bhatia P. K.
Published: July 2007

The dynamic instability of a composite hydromagnetic compressible plasma has been studied to include the effects of finite electrical conductivity. Making use of existence of the variational principle which is shown to characterize the problem, proper solutions have been obtained for a semi‐infinite composite plasma having density stratification along the vertical. It is found that the frictional effects with neutrals have a stabilizing influence on the growth rate of the unstable disturbances while compressibility as well as magnetic resistivity both have a destabilizing influence.
A Model for Diffuse Breakdown in High Pressure Gases at Homogeneous Electric Field Strengs
Authors: Gündel H.
Published: July 2007

A model of the breakdown in high pressure gases is presented taking into consideration the finite voltage rise time at the discharge electrodes and a finite initial charge carrier density in the gap. Several types of breakdown could be distinguished important for several applications. Thus, the range of existence of high pressure laser discharges at a given preionization density and circuit parameters can be calculated. Moreover, the change in the breakdown characteristics of high pressure gases at high temperatures is explained. This behaviour seems to be important for understanding the physical processes in circuit breaker chambers.
Modulational Instability of Two Longitudinal Waves in a Hot Electron Plasma
Authors: Das K. P. , Sihi S.
Published: July 2007

By Whitham's method of averaged Lagrangian two coupled nonlinear Schrödinger equations are derived that give the evolution of the amplitudes of two longitudinal waves, both propagating in the same direction in a hot electron plasma. It is found that a single wave is modulationally stable, while two waves together are modulationally unstable if either the difference between the group velocities of the two waves is sufficiently large, or if this difference is sufficiently small and a coefficient, which couples the two waves, is sufficiently large.
On the Nonlinear Resonances in Bounded Crossed Fields Plasma
Authors: Nikolov N. A. , Malinov P. N. , Ivanov S. T.
Published: July 2007

On the basis of the two‐component MHD and a full electromagnetic treatment, nonlinear resonances of bounded plasma placed in crossed external a.c. electric and constant magnetic fields are found.
Bestimmung der Ionendichte in strömenden Hochdruckplasmen mittels elektrischer Staupunktsonden
Authors: Lachmann J. , Winkelmann G.
Published: July 2007

Es wurde eine elektrische Staupunktsonde zur Messung lokaler Ionendichten in strömenden Hochdruckplasmen (p = 105 Pa) entwickelt. Die experimentellen Ergebnisse der im Raumladungs‐Konvektions‐Gebiet arbeitenden Sonde bestätigen die Richtigkeit der Sondentheorie bezüglich der Kennlinienform und der gemessenen Ionendichte, die mit spektroskopischen Werten verglichen wird. Die Abweichung zwischen beiden Meßverfahren ist geringer als eine halbe Größenordnung.
Van Kampen and Case Formalism Applied to Linear and Weakly Nonlinear Initial Value Problems in Unmagnetized Plasma
Authors: Lambert A. J. D. , Best R. W. B. , Sluijter F. W.
Published: July 2007

A unified account is given of the normal mode theory of homogeneous unmagnetized plasma. Electron (Langmuir), ion sound and electromagnetic waves are treated in stable and (Penrose) unstable plasma with the Van Kampen‐Case formalism, using generalized functions. Simplified formulae are derived for second‐order Langmuir waves, taking full account of free‐streaming effects.
Investigations of Impurity Atom Deposition in the Limiter Shadow of the T‐10 Tokamak by Means of Auger Electron Spectroscopy
Authors: Chicherov V. M. , Hildebrand D. , Laux M. , Lingertat J. , Lukianov S. U. , Pech P. , Reiner H.‐D. , Stepanchikov V. A. , Wolff H.
Published: July 2007

The impurity flux in the limiter shadow region of the T‐10 tokamak has been studied by exposing a solid probe to the plasma and subsequent investigation of deposits by surface analysis techniques.

The main constitutents of the inner construction materials of T‐10 could be detected by AES and SIMS. The deposited amount of impurities has been shown to rise with a decrease of the distance between probe and plasma. Long term observations of the metal impurity composition in the limiter shadow region by means of the deposition probe have shown a gradual decrease of the relative Ni concentration, which is explained as a successive deposition of stainless steel limiter material on the Inconel liner. The observed spatial asymmetry of the impurity flux and the deposition profiles for different elements on the probe are discussed.
Thomson Scattering Applied to a Noisy Radiative Plasma
Authors: van Der Sijde B. , Adema S. , De Haas J. , Denissen C. J. M. , van De Sande M. J. F.
Published: July 2007

Thomson scattering with a 1.5 ms long pulse mode 20 J ruby laser has been applied to a radiative argon plasma with electron densities ne from 2.5 1019 m−3 to 1.5 1020 m−3 and an electron temperature Te of about 3 eV. Photon counting techniques have been used. The accuracy of ne and Te to be reached is about 5% after 10 shots. The signal to noise ratio S/N has been optimized by the use of optical filters and a special purpose grating. The effects of these elements on S/N have been calculated. The entrance angle, transmission and quantum efficiency have also been optimized. A comparison between 5 possible laser systems, including a normal mode and a Q‐switched mode ruby laser, has been carried out.
Untersuchungen zu den Existenzbereichen und Typen von ac‐Entladungen. II. Das Verhalten der Entladungstypen in Ne/Ar‐Gemischen und der Vergleich mit Ne/N2‐Gemischen
Authors: Müller S. , Zahn R. J.
Published: July 2007

The investigations on the transition between the discharge modes in NeN2 mixtures are described in [1]. In the present paper we investigate NeAr mixtures with a view to comparing the behaviour of these different mixtures. The measurements confirm the transition mechanism between the bistable pulse mode and the non‐bistable continous mode in Ne‐Penning mixtures. The life time of metastable atoms is important for the existence of the continuous mode. If the life time is changed by varying the cross sections for the Penning ionization Qp (e.g. in other mixtures), the transition frequency of both these discharge modes shows a corresponding shift, which, for both mixtures, is in good agreement with literature values of Qp. The second part presents a study of the quasiglow mode. The transition between the pulse mode and the quasiglow mode correlates to the ion transit time. The three discharge modes are represented in the existence diagram.
Spektroskopische Untersuchung unelastischer Stöße zwischen Ionen oder metastabilen Atomen der Edelgase und Alkalimetallatomen bei thermischen Stoßenergien
Authors: Vogel D. , Tolmachev Yu. A.
Published: July 2007

The present work deals with the spectroscopic investigation of Penning ionization and nonresonant charge exchange due to thermal‐energy collisions of metastable atoms or ions of the inert gases He, Ne with atoms of alkali metals K, Rb, Cs in a low temperature plasma of the corresponding binary mixtures. The rate constants of these reactions and partial rate constants of exciting several alkali metal ion levels were determined by the kinetics of the decay of ionized and excited particles in the afterglow of a pulsed discharge. Measured Penning and charge exchange constants are in order of 1010‐9 cm3 sec−1. Partial Penning constants in the HeCs system exhibit a small dependence of the energy defect of reaction, whereby an important part of collisions results in excited Cs+‐states. On the contrary, energy transfer by charge exchange in HeRb, Cs systems distinguishes by a significant energy defect dependence. Charge exchange from He+ to Rb0 leads above all to He(23S1)‐atoms and normal Rb+‐ions. It follows from the metal ion spectrums, that Penning ionization and charge exchange of the investigated systems under utilized conditions represent as processes of selective excitation of alkali metal ions in afterglow and stationary discharge.
Magnetoplasma Lamination due to Microwave Gyroresonant Heating
Authors: Shvartsburg A. B.
Published: July 2007

The hysteresis transitions between two temperature states of a collisional magnetoplasa due to Joule heating near by the electron gyroresonance are analysed. The propagation of intense extra‐ordinary gyroresonant microwave across the magnetic field in a plasma is responsible for such jump‐like thermic effects, the wave amplitudes being less than the “characteristic plasma field”. The transversal heat conductivity may lead to formation of spatially periodical temperature profiles in the hysteresis region of wave's intensity; the spatial periods of such profiles are much less than the Joule dissipation length of heating wave. The thermodiffusion, stimulated by temperature lamination, may form the spatial oscillations of magneto‐plasma density across the magnetic field.
Formation of ac Discharges Between Glass Insulated Electrodes in Ne + 1% N2 Mixtures. I. Experiments and Analysis
Authors: Stern W. , Lange H.
Published: July 2007

Ac plasma displays make use of medium pressure ac discharges in Penning mixtures between insulated electrodes. Discharges in Ne + 1% N2 with glazed electrodes are a suitable experimental model showing the characteristic pulse and continous discharge modes. The axial optical space time structure of sinus wave sustained model discharges are measured with a scanning device, obtaining characteristic phases of discharge formation. Application of luminous flux method for stationary and dynamic Townsend discharges yields the first Townsend ionization coefficient α, and the comparison of the optical structure of ac discharges with that of dc discharges allows to explain the axial structure and to estimate the space charge effects.
Stability of a Self‐Gravitating Partially Ionized Plasma
Authors: Sankhla V. D. , Bansal J. L.
Published: July 2007

The dynamic stability of a stratified layer of a partially ionized, self‐gravitating plasma is studied to investigate the effects of finite electrical conductivity. The whole system is immersed in a uniform vertical magnetic field. It is first shown that the solution is characterized by a variational principle. An explicit solution has been then obtained for a semi‐infinite composite plasma in which the density has a one‐dimensional gradient along the vertical.

Numerical calculations show that the influence of neutral gas friction and self‐gravitation is stabilizing whereas character of finite electric conductivity is destabilizing.
Nonlinear Theory of the Instability of a Modulated Electron Beam of Low Density in a Plasma IV. Excitation of Nonresonant Waves
Authors: Kruscha K. J. G. , Kondratenko A. N.
Published: July 2007

A system of nonlinear equations derived in a previous paper which describes the evolution of nonresonant waves in beam‐plasma systems is solved numerically. It is given a physical interpretation of essential features of the nonresonant beam‐plasma instability. The significant influence of higher harmonics on the evolution of an electron beam in the plasma which is modulated on a nonresonant unstable frequency, is investigated. The interaction of unstable nonresonant and resonant waves in beam‐plasma systems is examined. It is shown that the evolution of resonant waves can be essentially influenced by an initial modulation of the beam on an unstable non‐resonant frequency. The role of an initial velocity modulation of the beam for the influence of the wave spectrum is demonstrated.
On the Relevance of Plasma Parameters in Nonideal Plasmas
Authors: Hess H.
Published: July 2007

The use of different plasma models for composition calculations of nonideal plasmas can result in very different electron concentrations for the same experimental situation characterized e.g. by the measured temperature and pressure. This gives rise to misunderstandings at comparison of theoretical and experimental results. For extreme conditions i.e. in the region of the supposed plasma phase transition results of solid state physics give us the possibility to rule out some plasma models.
Collisional‐Radiative Recombination in Argon Plasmas
Authors: Vľek J. , Ferdinand J.
Published: July 2007

On the basis of the realistic argon atom model consisting of 65 discrete effective levels numerical results for the collisional‐radiative volume recombination, ionization and decay coefficients are obtained. The computations are carried out without any approximations of integral functions. The presented comparison of theoretical and experimental results for the decay coefficient shows that the values calculated by us are in much better agreement with experimental values than those obtained by Desai and Corcoran on the assumption that the argon atom is hydrogen‐like.
Lokale Diagnostik einer Argon‐Niederdruckentladung mit Hilfe der resonanten Laserstreuung
Authors: Bergmann J. , Schubert M.
Published: July 2007

We report on the experimental investigations on a laser‐like low pressure argon gas discharge. The discharge parameters varied in the range from 0,05 to 1 Torr for the gas pressure and from 10 to 30 A for the discharge current.

Local electron densities and temperatures have been measured with an adjustable spherical probe.

Spatially resolved measurements of the temperatures and drift velocities of the Ar+‐ions in the radial and axial direction of the positive column have been carried out by the resonant laser light scattering (fluorescence technique).

The radial density profiles of the excited Ar+‐ions have been determined in two different ways and have been compared with the calculations based on a simple collisional radiative model.
Amplification of Ion‐Acoustic Solitary Waves in a Vlasov‐Plasma. I. A Higher Order Nonlinear Evolution Equation of KdV‐Type
Authors: Bruhn B. , Leven R.
Published: July 2007

With the help of an iterative method we derive a higher nonlinear evolution equation of the KdV‐type starting from the Vlasov‐Poisson system. This equation describes the amplification of ion‐acoustic solitary waves. A perturbative‐theoretical approach is given for small deviations from the 1‐soliton solution. The amplification shows an exponentiel time behaviour in this limit.
On the Plasma Beam Instability of the Space Limited Electron Beam in a Magnetic Field
Authors: Ivanov A. A. , Popkov N. G. , Wilhelm J. , Winkler R.
Published: July 2007

The present paper considers the plasma‐beam instability of a space limited electron beam in a strong magnetic field (ωH ≫ ωo). The form of the beam was taken to be both cylindrical and plane. The threshold of the non‐linear regime turned out to be weakly dependent on the beam form and independent of the magnetic field intensity. It is defined by the current and the directed velocity of the beam particles.
The Effect of Finite Larmor Radius on Gravitational Instability of a Finitely Conducting Magnetised Hall Medium in Presence of Suspended Particles
Authors: Chhajlani R. K. , Purohit P.
Published: July 2007

The problem of stability of a self‐gravitating, infinite homogeneous gas in the presence of suspended particles is investigated. The medium is assumed conducting and effect of external magnetic field, Hall current and finite Larmor radius corrections are also considered. The equations of the problem are linearized and from linearized equations a general dispersion relation for a dusty gas‐particle medium is obtained. The dispersion relation is reduced for two special cases of wave propagations: Parallel and perpendicular to the direction of uniform magnetic field. The effect of suspended particles on the medium is investigated in both the cases. It is found that in the presence of finite Larmor radius corrections and suspended particles the condition of instability is determined by Jeans's criterion for a self gravitating finitely conducting magnetised Hall medium.
On the Symmetrical Modes in a Cylindrical Nonisothermal Plasma Waveguide in a Finite External Magnetic Field
Authors: Nikolov N. A. , Yanovsky A. B.
Published: July 2007

A MHD, symmetrical, nonpotential waves in nonuniform, cylindrical nonisothermal plasma waveguide placed in a finite external magnetic field H0 directed along the axis of the waveguide are considered. The thermal velocity of the electrons νTe = (kTe/me)1/2 (k — Boltzman's constant, Te — temperature, me — mass of the electron) is not neglected. As a consequence we obtain one more solution in the plasma region and respectively an equation of third power on χ2 — the transverse wave number. As far as we know only equations of second power on χ2 describing non‐potential waves are investigated. The dispersion equations are written solving the boundary‐value problem. Our results coincide with well known ones when the electron thermal velocity tends to zero.
Electron Kinetics of Weakly Ionized HF Plasmas I. Direct Treatment and Fourier Expansion
Authors: Winkler R. , Deutsch H. , Wilhelm J. , Wilke Ch.
Published: July 2007

In this paper an analysis of the kinetic quantities of the electrons in the steady‐state HF neon plasma is performed by a time consuming direct solution of the time dependent electron Boltzmann equation up to the establishment of the periodic state. In particular, the reduction of the modulation degree and the phase shift with respect to the HF field of the isotropic distribution function and of some macroscopic electron quantities are systematically determined with increasing field frequency. Furthermore, using the Fourier expansion technique, an equation system for the Fourier coefficients of the isotropic distribution function was derived from the time dependent Boltzmann equation which immediately gives a description of the electron kinetics in the steadystate HF plasma. On the basis of this system the coupling of the harmonics of the isotropic distribution with its dc part was studied for different HF fields. In addition, appropriate conditions could be found which determine a field frequency limit above which the coupling impact of the harmonics on the determination of the dc part of the isotropic distribution may be neglected, making a simplified treatment of the electron kinetics possible. The exact determination of its validity limits and the systematic investigations on the basis of this simplified kinetics will be reported in a second paper.
Collisional Radiative Models in Plasmas
Authors: Van Sijde B. Der , van der Mullen J. J. A. M. , Schram D. C.
Published: July 2007

A review on collisional‐radiative models in plasmas is given. Work of Fujimoto, Biberman et al, Drawin and Seaton has been an important guide to compose this review. Ionizing, recombining and equilibrium plasmas are dealt with. Attention has been paid to the classification of CR models in phases, such as Corona phase, excitation saturation phase (ESP), Capture radiative cascade (CRC) phase and partical local thermal equilibrium (PLTE). A numerical model applied to the argon neutral system and an analytical model applied to the ESP and PLTE for ionizing plasmas are treated in more detail.
On the Quantitative Determination of Cross Sections of Ionization of Molecules by Electronic Collisions
Authors: Deutsch H. , Schmidt M.
Published: July 2007

It is tested the applicability of formulae for atomic ionization to molecules. The best fit between theoretical and experimental values is given by the formula of Gryzinski. The calculations require the knowledge of the orbital structure.

If no detailed information on electronic molecular structure is available, then approximation is attained using the Lotz formula with three fitting parameters.

Results are given especially for organic molecules and Cl and F contaning etching gases.
Three Coupled Nonlinear Schrödinger Equations for Two Transverse and One Langmuir Waves and the Stability of Their Solitary Wave Solutions
Authors: Bhakta J. C. , Majumder D.
Published: July 2007

Three Coupled nonlinear Schrödinger equations for two transverse and one longitudinal waves has been derived. These equations have been derived using two space time scale techniques. It is shown that even without the effect of relativistic mass variation and ion contribution, all three waves may propagate in the form of localized solitary envelope with a common velocity for small values of the transverse wave numbers and the longitudinal wave number far exceeding kD√me/mi. Stability analysis of the localized solitary wave form reveals that these wave forms are stable.
On the Kinetics of the Active Zone of the Stationary SF6 Beam Discharge Plasma
Authors: Winkler R. , Wilhelm J. , Ivanov A. A. , Popkov N. G.
Published: July 2007

The paper deals with the impact of intensive electron attachment on the kinetics of the electrons in the active zone of the stationary band‐like beam discharge plasma in SF6 which is an alternative useful plasma medium for “dry etching”. The energy distribution of the electrons in this plasma was obtained by numerically solving the Boltzmann equation which includes apart from elastic collisions, different exciting collision processes, attachment in electron collisions, direct ionization, the ambipolar loss of electrons, Coulomb interaction between electrons and of electrons with ions and the power input to the electrons by the turbulent electric field. In particular, due to the needed fulfilment of the consistent electron particle balance, for an extended region of the turbulence energy density in this plasma a large impact on the electron kinetics of the intensive electron attachment, which is the prevailing electron loss process, was found enforcing independent of the turbulence energy density always a large power input to the electrons, smooth and only slowly decreasing energy distributions even in the energy region of direct ionization.
Theory of Thermal Fluctuations for Leaking and Non Leaking Surface Waves
Authors: Uddholm P.
Published: July 2007

Thermal fluctuation spectra are discussed for electromagnetic waves in magnetized, inhomogeneous, cold electron fluid plasmas.
The Model of Macroscopic Kinetics in Non‐Equilibrium Plasma Chemical Reactions I. General Considerations and Basic Relations
Authors: Rutscher A. , Wagner H. E.
Published: July 2007

The reaction of a chemical active non‐equilibrium plasma system is studied within simple kinetic models in principle.

Of special interest are steady states of the system with the meaning of a reversible chemical equilibrium.

Starting from a schematized description of the non‐isothermal plasma chemical reactor the basic relations of the so‐called macroscopic kinetics are developed and in the case of a comprehensive example (synthesis and decomposition of ozone) compared with the corresponding microscopic kinetics.
Collision Frequencies for Electrical and Heat Conductivity in Dense Cold Plasmas
Authors: Suchy K.
Published: July 2007

Formulas for electrical and heat conductivity are derived from the Boltzmann equation with Grad's method of orthogonalized moments, retaining the coupling between diffusion and heat fluxes. The results are expressed by transport collision frequencies. These are calculated for Coulomb interaction potentials screened with the Debye‐Hückel length. Quantum corrections to the classical results are included.
Inversion of the Abel Integral Equation by Use of Simple Interpolation Formulas
Authors: Sato M.
Published: July 2007

The Abel integral equation in plasma spectroscopy is numerically solved by applying the Bessel four‐point interpolation formula of degree two. The method is mathematically tractable, simplifying the Bockasten method. Tests through numerical simulations show that the method is as accurate as more elaborate methods, such as Bockasten, Minerbo‐Levy, Piessens, etc.
Long Time Behaviour of the Modulational Instability of Zakharov Equations
Authors: Majumdar D. , Bhakta J. C.
Published: July 2007

The long time behaviour of the modulational instability of a monochromatic Langmuir wave solution E0 exp i (k0x − ω0t) of the Zakharov equations has been investigated. It is shown that near the threshold of linear instability the evolution of the modulational perturbation is governed by the nonlinear Schrödinger equation and thus the possibility of the development of the modulation into a train of soliton is established. In case of a purely growing modulational perturbation the long time behaviour of the perturbation is suggestive of a Fermi‐Pasta‐Ulam recurrence tendency.
Experimental Study of Ionization Waves in the contracted Discharge in Neon
Authors: Golubovskij Ju. B. , Nekuchajev V. O.
Published: July 2007

It is proved experimentally that there exist constriction ionization waves propogating in the form of current pinch neckings. Dynamics of abrupt contraction and strate arising is investigated by current modulation near the critical value. Dispersion laws are determined depending on discharge conditions.
The Gravitational Instability of a Finitely Conducting Rotating Plasma Through a Porous Medium
Authors: Chhajlani R. K. , Sanghvi R. K.
Published: July 2007

The magneto‐gravitational instability of an infinite homogeneous, finitely conducting, viscous rotating plasma through porous medium is investigated in view of its relevance to certain stellar atmospheres. The dispersion relation has been obtained from the relevant linearized perturbation equations of the problem and it has been discussed in the case of rotation parallel and perpendicular to the direction of magnetic field separately. The longitudinal and transverse modes of wave propagation are discussed in each case of rotation. It is found that the combined effect of viscosity, finite conductivity, rotation and the medium porosity does not essentially change the Jeans' criterion of gravitational instability. It is also shown that for the propagation transverse to the direction of magnetic field. the finite conductivity destabilizes the wave number band which is stable in the limit of infinite conductivity when the medium is considered inviscid.
Study of the Balmer Spectrum of Hydrogen from a High‐Pressure Arc Discharge. I. Spectroscopic Measurements and Plasma Analysis
Authors: Radtke R. , Günther K.
Published: July 2007

The Balmer spectrum of hydrogen emitted from a wall‐stabilized pulse discharge has been measured covering a pressure range between 0.1 and 1.2 MPa. The temperature achieved in the discharge varied between 13000 and 22000 K corresponding to a variation in the electron concentration between 1023 and 1024 m−3.

Special consideration is given to the problems in both diagnostics and spectroscopic data acquisition.
Study of the Balmer Spectrum of Hydrogen from a High‐Pressure Arc Discharge. II. Comparison of Experiment and Theory
Authors: Radtke R. , Günther K. , Spanke R.
Published: July 2007

The intensity distribution in the Balmer spectrum of hydrogen was calculated in the context of a model in which a cut‐off Coulomb potential is applied to simulate the influence of the surrounding plasma on the spectral distribution of atomic oscillator strengths. The results show satisfactory over‐all agreement with experimental data obtained from a high‐pressure are discharge.
Ein Differenzmeßverfahren zur sehr genauen Bestimmung der Güte und Resonanzfrequenz von Mikrowellenresonatoren durch Amplitudenmodulation des Meßsignals
Authors: Gundermann S.
Published: July 2007

In diesem Beitrag wird ein Differenzmeßverfahren angegeben, das eine sehr genaue Bestimmung der Resonanzfrequenz und Resonatorgüte auch von stark belasteten Mikrowellenresonatoren ermöglicht.
A Thermodynamics Approach to the Deflected Wall‐Stabilized Electric Arc Return Process
Authors: Ramos‐Barrado J. R.
Published: July 2007

The return of a deflected wall‐stabilized electric arc to the axial position is studied as a relaxation process within the framework of the after‐effects theory. The arc displacement is defined as an internal thermodynamics parameter and the determination of the affinity of this process was based on relaxation characteristic time.
Mode Transition of Ionization Waves in Non‐Uniform Magnetic Field
Authors: Maruyama T. , Ozawa T. , Mizuochi H. , Kitamura H. , Itagaki K.
Published: July 2007

Experimental observations on mode transition in a positive column of Ne gas under non‐uniform axial magnetic field are reported. The self‐excited ionization wave is damped and a different type of ionization wave is grown in the region of the strong magnetic field near the magnetic coils. The mode transitions appear on both sides of the magnetic coils where the magnetic field crosses a critical value.
Measurements of Temperature and Electron Density Distributions in a Helium Plasma Produced Near Ceramic Surface
Authors: Musielok J.
Published: July 2007

The temperature and electron density distributions in a helium plasma produced near ceramic surfaces at atmospheric pressure have been studied. The determination of these plasma parameters is based on spatial resolved line intensity measurements.
Possible High Power Laser Construction Using a New Discharge Type‐Heated Cathode Discharge in the Copper Vapours Continuously Evaporated from the Anode
Authors: Musa G. , Baltog A. , Popescu A. , Betiu N. , Mustata I.
Published: July 2007

The possibility to build a high power copper laser using a new type of discharge – heated cathode discharge in the copper vapours continuously evaporated from a melted spot on the anode surface is analysed.

From the experimental data on this new discharge type, the equivalent pressure of the copper atoms in the discharge space has been obtained. This pressure can be as high as 1 torr. The density of the power in the discharge volume is evaluated to be more than 1 kW/cm3.
Targeted cell‐ablation in Xenopus embryos using the conditional, toxic viral protein M2(H37A)
Authors: Smith Stuart J. , Kotecha Surendra , Towers Norma , Mohun Timothy J.
Published: July 2007

Harnessing toxic proteins to destroy selective cells in an embryo is an attractive method for exploring details of cell fate and cell–cell interdependency. However, no existing “suicide gene” system has proved suitable for aquatic vertebrates. We use the M2(H37A) toxic ion channel of the influenza‐A virus to induce cell‐ablations in Xenopus laevis. M2(H37A) RNA injected into blastomeres of early stage embryos causes death of their progeny by late‐blastula stages. Moreover, M2(H37A) toxicity can be controlled using the M2 inhibitor rimantadine. We have tested the ablation system using transgenesis to target M2(H37A) expression to selected cells in the embryo. Using the myocardial MLC2 promoter, M2(H37A)‐mediated cell death causes dramatic loss of cardiac structure and function by stage 39. With the LURP1 promoter, we induce cell‐ablations of macrophages. These experiments demonstrate the effectiveness of M2(H37A)‐ablation in Xenopus and its utility in monitoring the progression of developmental abnormalities during targeted cell death experiments. Developmental Dynamics 236:2159–2171, 2007. © 2007 Wiley‐Liss, Inc.
Cited1 and Cited2 are differentially expressed in the developing kidney but are not required for nephrogenesis
Authors: Boyle Scott , Shioda Toshi , Perantoni Alan O. , de Caestecker Mark
Published: July 2007

Early kidney development in mammals is characterized by reciprocal tissue interaction between the ureteric bud and the metanephric mesenchyme. The coordinated response to this interaction is regulated largely at the transcriptional level. Here, we investigate the expression and function of Cited1, a transcriptional cofactor that we have previously implicated in kidney development. We show that Cited1 is expressed in the metanephric mesenchyme after invasion of the ureteric bud and that its expression is limited to the cap mesenchyme, those cells that aggregate most tightly around the tip of the ureteric bud and give rise to nephronic epithelium of the adult kidney. Cited1 is down‐regulated during the initial stages of epithelial conversion and is not expressed past this progenitor stage. Despite its unique expression pattern, deletion of Cited1 does not disrupt kidney development. We hypothesized that this finding was due to functional redundancy with other members of this gene family. The expression pattern of Cited2 overlaps that of Cited1, but its deletion, either alone or in combination with Cited1, does not disrupt epithelial differentiation of the metanephric mesenchyme. From these studies, we conclude that Cited1 and 2 are dynamically expressed during kidney development, but are not required for nephrogenesis. Developmental Dynamics 236:2321–2330, 2007. © 2007 Wiley‐Liss, Inc.
The diabetogenic, insulin‐specific CD8 T cell response primed in the experimental autoimmune diabetes model in RIP‐B7.1 mice
Authors: Karges Wolfram , Rajasalu Tarvo , Spyrantis Andreas , Wieland Andreas , Boehm Bernhard , Schirmbeck Reinhold
Published: July 2007

Type 1 diabetes mellitus can result from the specific destruction of pancreatic beta cells by autoreactive T cells. As shown here, experimental autoimmune diabetes (EAD) is efficiently induced in RIP‐B7.1 mice by preproinsulin (ppins)‐encoding DNA vaccines. EAD develops in RIP‐B7.1 mice within 3–4 wk after a single immunization with ppins‐encoding plasmid DNA. RIP‐B7.1 mice develop insulitis, insulin deficiency and hyperglycemia after vaccination with plasmids encoding murine ppins‐I or murine ppins‐II or human hu‐ppins. EAD induction critically depends on CD8 T cells and is independent of CD4 T cells. To be diabetogenic, ppins‐specific CD8 T cells had to express IFN‐γ. Neither expression of perforin nor signaling through the type I IFN receptor is an essential component of this pathogenic CD8 T cell phenotype. Using plasmids encoding truncated ppins variants, we show that EAD is only induced by DNA vaccines encoding the insulin A‐chain. Diabetogenic CD8 T cells specifically recognize the Kb‐restricted A12–21 epitope of the insulin A‐chain. The RIP‐B7.1 model hence represents an attractive model for the characterization of cellular and molecular events involved in the CD8 T cell‐mediated immune pathogenesis of diabetes.
Alkyl Chain Length Defines 2D Architecture of Salophen Complexes on Liquid–Graphite Interface
Authors: Räisänen Minna T. , Mögele Florian , Feodorow Santeri , Rieger Bernhard , Ziener Ulrich , Leskelä Markku , Repo Timo
Published: July 2007

A series of CuII, NiII and CoII salophen [salophen = N,N′‐(o‐phenylene)bis(salicylideneimine)] complexes were prepared, and their two‐dimensional (2D) assemblies on a liquid–graphite interface were studied by scanning tunnelling microscopy (STM). Depending on their varying alkyl chain lengths (C8, C10 or C12), two different new adlayers, parallelogram and honeycomb, were recorded. According to STM data, the driving force for these assemblies is a subtle interplay between a maximum amount of attractive van der Waals interaction of the alkyl chains and weak hydrogen bonding of the phenoxy moieties. Thus, the alkyl chain length defines the favoured 2D structure for each metal complex. As shown here, the self‐assembled monolayers of the salophen complexes studied provide an attractive approach to varying the surface architecture.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Photochemical Arylation Reactions by 4‐Chlorothioanisole
Authors: Lazzaroni Simone , Dondi Daniele , Fagnoni Maurizio , Albini Angelo
Published: July 2007

The photochemistry of 4‐chlorothioanisole (1) was investigated in various solvents, and it was found to involve the reduction to thioanisole as the main process. This occurs by heterolytic fragmentation of the triplet state of 1 and formation of the triplet 4‐thiomethoxyphenylium ion, as supported by DFT calculations. The cation is trapped by alkenes and, less efficiently, by benzene, resulting in new examples of the recently emerging arylation reactions by SN1 substitution of phenyl halides. The products from alkenes involve the phenonium ion as a further intermediate. The product distribution differs from the analogous reactions via 4‐methoxyphenylium for including a larger proportion of 4‐(β‐substituted alkyl)‐ rather than 4‐allylthioanisoles derivatives in alcohols, for the lower fraction of rearranged α‐substituted 4‐alkylthioanisoles and for the formation of some 4‐cyclopropylthioanisole with allyltrimethylsilane. The difference is accounted for by the more developed dipolar character of the C–C cyclopropane bonds in the intermediate phenonium, as indicated by DFT calculations.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
A New Conformationally Restricted Mimetic of Dipeptide EG – Synthesis of an Analogue of FEG
Authors: Galeazzi Roberta , Martelli Gianluca , Marcucci Eleonora , Mobbili Giovanna , Natali Desiré , Orena Mario , Rinaldi Samuele
Published: July 2007

Starting from the chiral pyrrolidin‐2‐one 2, the carboxy group at C‐4 underwent homologation, and subsequent removal of the 1‐(4‐methoxyphenyl)ethyl group gave lactam 6. Alkylation of N‐1 with benzyl bromoacetate led to 7, a new conformationally restricted analogue of the dipeptide EG (Glu‐Gly). The usefulness of 7 was demonstrated by its eventual conversion into 8, an orthogonally protected analogue ofbioactive tripeptide FEG. In order to provide the biological activity of the new mimetic 9, available from 8 after the removal of the protecting groups, the conformational preference of 9 was ascertained by a detailed conformational analysis and a comparison with that of FEG (1). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Synthesis, Characterization and Electrochemical Polymerization of a Ru2+ Functionalized Pyrrole Monomer
Authors: Foster Kevin , McCormac Timothy
Published: July 2007

A ruthenium(II) functionalized pyrrole, Ruthenium‐bis‐N,N′‐(2,2′‐bipyridyl)‐N‐(pyridine‐4‐ylmethyl‐(8‐pyrrole‐1‐yl‐octyl)amine)chloride, 1, has been synthesized and characterized by spectroscopic (UV/vis, 1H NMR) techniques and cyclic voltammetry. In solution 1 gave a redox couple associated with the Ru3+/2+ redox system and an irreversible wave associated with the oxidation of the covalently linked pyrrole moiety. What is believed to be homopolymerization, redox active surface films of 1 have been prepared by electrooxidation of the monomeric solution. The resulting polymeric film exhibited clear redox activity associated with the incorporated Ru2+ redox centre, which is covalently linked ruthenium centre to the pyrrole moiety in 1. The effect of surface coverage upon the electrochemical behavior of the deposited films has been undertaken. Preliminary investigations into the homogeneous charge transport dynamics of the polymeric film deposited onto platinum microelectrodes has been undertaken. Copolymerization with 3‐methylthiophene was carried out and a clear ruthenium response was seen. Films were formed by both cyclic voltammetry and chronocoulometry and studied. Various ratios were attempted but the ideal was found to be 52 : 5 mmol (3‐methylthiophene: 1).
Detection of Sulfur Microparticles in Bacterial Cultures by Flow Cytometry
Authors: Hübschmann T. , Vogt C. , Till S. , Rohwerder T. , Sand W. , Harms H. , Müller S.
Published: July 2007

Repeated flow cytometric analyses of population shifts within a bacterial consortium growing under sulfate‐reducing conditions revealed unexpected and quick changes in forward scatter vs. side scatter dot plot patterns within less than 30 minutes of exposure to air. These pattern changes proceeded differently when cells were cultivated either at 30 °C or 12 °C. It was found that prominent sub‐distributions, clustering profoundly in size and number of events with time, represented sulfur particles and not microbial cells. Therefore, any interpretation of flow cytometric analyses of live bacteria grown under sulfate‐reducing conditions requires specific caution since sulfur particles might cause errors in data interpretation. To prevent artefacts, distinct treatments of the sample are recommended.
Analysis of an Anaerobic Chemostat Population Stably Dechlorinating 2,4,6‐Trichlorophenol
Authors: Breitenstein A. , Andreesen J. R. , Lechner U.
Published: July 2007

2,4,6‐Trichlorophenol (2,4,6‐TCP) was extensively used in the past as a component of various pesticide formulations as well as a wood preservative and, therefore, is ubiquitously present in the environment. It is also formed during the disinfection of drinking water sources or during wastewater treatment and is frequently detected in sewage sludges. Under anaerobic conditions, reductive dehalogenation is the most promising biological process for its detoxification. Here, an anaerobic, 2,4,6‐TCP ortho‐dehalogenating mixed culture is described, which was originally enriched from a Saale river sediment. In order to be able to analyze the capacity of this dechlorination process for the removal of 2,4,6‐TCP, a steady‐state continuous culture was grown over a period of 270 days under an N2‐CO2 (80:20) gas atmosphere in a chemostat using formate as an electron donor and 2,4,6‐trichlorophenol (2,4,6‐TCP) as an electron acceptor. 2,4,6‐TCP was dechlorinated via 2,4‐dichlorophenol (2,4‐DCP) to 4‐chlorophenol (4‐CP) liberating two chlorine atoms per molecule of 2,4,6‐TCP as chloride. Per mol of chloride, 2.2 mol of formate were consumed and 0.17 mol of acetate formed. When yeast extract (0.01 %) was omitted from the cultivation medium, 2,4‐DCP accumulated in the chemostat, suggesting that the components in the yeast extract were essential for reductive dechlorination. A second fermentation was performed over a period of 130 days in the absence of CO2 in the gas atmosphere and of carbonate in the cultivation medium, resulting in a slightly higher specific dechlorination rate, a higher requirement for formate, and a lower protein yield, indicating that formate was used as a sole carbon source for growth. The dilution rate (D) was continuously increased, leading to an increase of the dechlorination velocity up to 400 μmol Cl–/L h, a maximum specific dechlorination rate of 0.48 μmol Cl–/L min (mg protein) and a yield of 5.1 g protein/(mol Cl– released). The microbial community structure of the mixed culture was investigated by amplified ribosomal DNA restriction analysis (ARDRA), sequencing, and hybridization with species specific oligonucleotide probes. The dechlorinating bacterium Desulfitobacterium hafniense was found to be a dominant member of the mixed chemostat culture. Further members of the chemostat culture were detected by comparative analysis of the restriction patterns and sequencing and identified as bacteria most closely related to strains of Sedimentibacter, Clostridium propionicum, and Pseudomonas aeruginosa.
The suitability of different FEA models for studying root fractures caused by wedge effect
Authors: Meira Josete B. C. , Quitero Mayra F. Z. , Braga Roberto R. , Placido Eliane , Rodrigues Flávia P. , Lima Raul G. , Ballester Rafael Y.
Published: July 2007

Finite element analysis (FEA) utilizing models with different levels of complexity are found in the literature to study the tendency to vertical root fracture caused by post intrusion (“wedge effect”). The objective of this investigation was to verify if some simplifications used in bi‐dimensional FEA models are acceptable regarding the analysis of stresses caused by wedge effect. Three plane strain (PS) and two axisymmetric (Axi) models were studied. One PS model represented the apical third of the root entirely in dentin (PS‐nG). The other models included gutta‐percha in the apical third, and differed regarding dentin–post relationship: bonded (PS‐B and Axi‐B) or nonbonded (PS‐nB and Axi‐nB). Mesh discretization and material properties were similar for all cases. Maximum principal stress (σmax) was analyzed as a response to a 165 N longitudinal load. Stress magnitude and orientation varied widely (PS‐nG: 10.3 MPa; PS‐B: 0.8 MPa; PS‐nB: 10.4 MPa; Axi‐B: 0.2 MPa; Axi‐nB: 10.8 MPa). Axi‐nB was the only model where all σmax vectors at the apical third were perpendicular to the model plane. Therefore, it is adequate to demonstrate the tendency to vertical root fractures caused by wedge effect. Axi‐B showed only part of the σmax perpendicular to the model plane while PS models showed σmax on the model plane. In these models, σmax orientation did not represent a situation where vertical root fracture would occur due to wedge effect. Adhesion between post and dentin significantly reduced σmax. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2008