bluuebunny/crossref_metadata_2025 huggingface dataset:
Phosphidtelluriden auf der Spur: Zum System Ce/Te/P. The Trace to Phosphide Tellurides: The System Ce/Te/P
Authors: Philipp Frauke , Pinkert Katja , Schmidt Peer
Published: March 2009

The cerium phosphide tellurides Ce3Te4–xPx (x ≤ 1), CeTe2–xPx (x ≈ 0.35–0.55) and CeTe2–yPy (y ≥ 1) have been synthesised from the elements or from oxides in a thermite‐type reaction. Both ways have been optimised by consideration of the thermodynamic behaviour of the compounds. Hence the investigation of phase equilibria in the ternary system Ce/Te/P and of the thermal decomposition of ternary phases was necessary. This investigation was performed by using different experimental approaches as total‐pressure measurements and thermal analysis. It was shown that the cerium phosphide tellurides decompose in consecutive steps into CeTe(s) and gaseous phosphorus, [P4(g)]. The results were supported and further analysed by thermodynamic modelling of the ternary system; the computed phase diagrams of the systems Ce/Te and Ce/Te/P are presented.
Structure and Optical Properties of the Arsenide Oxides REZnAsO (RE = Y, La–Nd, Sm, Gd–Er)
Authors: Lincke Hannes , Glaum Robert , Dittrich Volker , Möller Manfred H. , Pöttgen Rainer
Published: March 2009

The equiatomic rare earth metal zinc arsenide oxides REZnAsO (RE = Y, La–Nd, Sm, Gd–Er) were synthesized in well crystallized form from the elements, arsenic, and ZnO in NaCl/KCl fluxes in sealed silica ampoules. The samples were characterized by powder and single‐crystal X‐ray data. HoZnAsO and ErZnAsO are reported for the first time. Four structures (ZrCuSiAs type, space group P4/nmm) were refined from single‐crystal X‐ray diffractometer data: a = 394.23(3), c = 884.0(1) pm, wR2 = 0.0345, 216 F2 values for YZnAsO, a = 409.56(3), c = 907.0(1) pm, wR2 = 0.0502, 285 F2 values for LaZnAsO, a = 397.62(4), c = 889.2(2) pm, wR2 = 0.0700, 216 F2 values for GdZnAsO, and a = 392.72(3), c = 881.5(1) pm, wR2 = 0.0580, 373 F2 values for ErZnAsO with 12 variables per refinement. The REZnAsO structures consist of alternate stacks of (RE3+O2–) and (Zn2+As3–) layers with covalent RE–O (224 pm in ErZnAsO) and Zn–As (255 pm in ErZnAsO) intralayer and weak ionic interlayer bonding. Both layers consist of condensed edge‐sharing OEr4/4 and ZnAs4/4 tetrahedra. In agreement with an electron precise formulation RE3+Zn2+As3–O2–, the crystals are transparent with yellow (LaZnAsO) to red color tones. In agreement with the different colors, LaZnAsO shows a significantly higher optical bandgap of Eg ≈ 2.3 eV than arsenide oxides REZnAsO (RE = Y, Pr, Nd, Sm) (Eg ≈ 1.9 eV).
High Temperature Phase and Thermal Expansion of PrBr3
Authors: Krämer Karl W. , Keller Lukas
Published: March 2009

The thermal expansion and phase transition of PrBr3 was investigated by neutron diffraction and DSC measurements. PrBr3 has a low‐temperature (LT) UCl3‐type modification and a high‐temperature (HT) PuBr3‐type modification. The stability range and structure of the HT phase were established for the first time by diffraction experiments. The thermal expansion of the LT modification was investigated by powder neutron diffraction from 1.6 K to 940 K. It shows a very anisotropic expansion of 3.5 % along the a‐axis up to 940 K, but along the c‐axis a small expansion of 0.14 % up to 445 K is followed by a contraction about 0.4 % up to 940 K. On heating, the LT phase is observed up to the melting point at 962 K. A partial transformation to the HT phase takes place above 956 K. On cooling, the HT phase crystallises from the melt at 946 K and transforms to the LT phase at 930 K.
Synthesis and Characterization of Mononuclear and Dinuclear Manganese Bis‐acetylide Complexes
Authors: Fritz Thorsten , Schmalle Helmut W. , Blacque Olivier , Venkatesan Koushik , Berke Heinz
Published: March 2009

The symmetric d5 trans‐bis‐alkynyl complexes {Mn[(Me)2P(CH2)nP(Me)2]2(C≡CC6H4R)2} (n = 2, R = ‐C≡CTIPS (2a); n = 3, R = ‐C≡CTIPS (2b); n = 2, R = F (4); n = 3; ‐C≡CTIPS) were prepared by the reaction of [Mn(dmpe)2Br2] with two equivalents of the corresponding acetylide LiC≡CC6H4R (R = F, ‐C≡CTIPS). The reaction of compounds 2a, 2b and 4 with [Cp2Fe][PF6] yielded the corresponding d4 complexes {Mn[(Me)2P(CH2)nP(Me)2]2(C≡CC6H4R)2}[PF6] (n = 2, R = ‐C≡CTIPS, [2a]+; n = 3, R = ‐C≡CTIPS, [2b]+;n = 2, R = F, [4]+; n = 3; ‐C≡CTIPS). The unsymmetrically substituted trans‐iodo‐alkynyl complex [IMn(dmpe)2(C≡CC6H4‐C≡CTIPS)] (5) was obtained by treating MeCpMn(dmpe)I with one equivalent of H‐C≡CC6H4‐C≡CTIPS in the presenceof dmpe. Deprotection of the TIPS group with TBAF gavecomplex [IMn(dmpe)2(C≡CC6H4C≡CH)] (6) in 94 % yield. The neutral dinuclear complexes MnII/MnII compounds {[Mn((Me)2P(CH2CH2)P(Me)2)2(C≡CC6H4R)]2(μ‐C4)} (R = H, Me, n‐pentyl, F) were prepared by the direct reaction of {[Mn((Me)2P(CH2CH2)P(Me)2)2I]2(μ‐C4)} with the corresponding LiC≡CC6H4R (R = H, n‐pentyl, F). These MnII/MnII dinuclear compounds were further oxidized to the mixed‐valent complexes and the dicationic complexes using [Cp2Fe][PF6]. All complexes have been characterized by NMR, IR, and Raman spectroscopy. X‐ray diffraction studies were carried out on complexes 1c, 2a, 4, [4]+, and 6.
A formal framework for modeling and validating Simulink diagrams
Authors: Chen Chunqing , Dong Jin Song , Sun Jun
Published: March 2009

Simulink has been widely used in industry to model and simulate embedded systems. With the increasing usage of embedded systems in real-time safety-critical situations, Simulink becomes deficient to analyze (timing) requirements with high-level assurance. In this article, we apply Timed Interval Calculus (TIC), a real-time specification language, to complement Simulink with TIC formal verification capability. We elaborately construct TIC library functions to model Simulink library blocks which are used to compose Simulink diagrams. Next, Simulink diagrams are automatically transformed into TIC models which preserve functional and timing aspects. Important requirements such as timing bounded liveness can be precisely specified in TIC for whole diagrams or some components. Lastly, validation of TIC models can be rigorously conducted with a high degree of automation using a generic theorem prover. Our framework can enlarge the design space by representing environment properties to open systems, and handle complex diagrams as the analysis of continuous and discrete behavior is supported.
Thymic Neuroendocrine Tumors in Multiple Endocrine Neoplasia Type 1: A Comparative Study on 21 Cases Among a Series of 761 MEN1 from the GTE (Groupe des Tumeurs Endocrines)
Authors: Goudet Pierre , Murat Arnaud , Cardot‐Bauters Catherine , Emy Philippe , Baudin Eric , du Boullay Choplin Hélène , Chapuis Yves , Kraimps Jean‐Louis , Sadoul Jean‐Louis , Tabarin Antoine , Vergès Bruno , Carnaille Bruno , Niccoli‐Sire Patricia , Costa Annie , Calender Alain ,   The members of the GTE network (Groupe des Tumeurs Endocrines)
Published: March 2009

Background

Thymic neuroendocrine tumors (Th‐NET) present a poor prognosis for patients with multiple endocrine neoplasia type 1 (MEN1). The purpose of this article was to study the clinical, biological, and pathological features of Th‐NET in a large cohort of patients with MEN1.

Methods

The 761‐patient MEN1 cohort from the GTE registry was used (Groupe des Tumeurs Endocrines).

Results

The actuarial probability of occurrence was 2.6% (range, 1.3–5.5%) at aged 40 years. All, except one, Th‐NET patients were men. Four patients had no other associated lesions. The youngest patient was aged 16 years. Mean age at the time of diagnosis was 42.7 (range, 16.1–67.5) years. The 10‐year probability of survival was 36.1% (range, 11.5–62%). Seven patients (33%) belonged to clustered MEN1 families. The spectrum of associated lesions in patients with Th‐NET was not statistically different from the spectrum of the remainder of the cohort. Various endocrine markers were high, but none were sensitive or specific enough to be useful for Th‐NET detection. CT‐scan and MRI were always positive at the time of diagnosis. No particular mutation was found to be associated with Th‐NET. Five cases underwent prophylactic thymectomy without success.

Conclusions

Several end points may be helpful for future guidelines: (1) earlier detection of Th‐NET in MEN1 patients is required; (2) screening of both sexes is necessary; (3) a prospective study comparing MRI vs. CT scan in yearly screening for Th‐NET is needed; (4) a reinforced screening program must be established for patients who belong to clustered families; and (5) thymectomies must be performed in specialized centers.
SAS Weekly Rounds: Avascular Necrosis
Authors: Hamilton Thomas W. , Goodman Susan M. , Figgie Mark
Published: March 2009

Osteonecrosis of the femoral head is a condition that affects upwards of 10,000 individuals in the USA each year. The peak incidence is in the fourth decade of life, and overall, there is a male preponderance. The condition accounts for up to 12% of total hip arthroplasties performed in developed countries. The etiology can be traumatic or non-traumatic, with 90% of atraumatic cases attributed to corticosteroid therapy or excess alcohol consumption. Osteonecrosis of the femoral head reflects the final common pathway of a range of insults to the blood supply and ultimately results in femoral head collapse, acetabular involvement, and secondary osteoarthritis. Currently, conservative treatment options, which aim to correct pathophysiologic features allowing revascularization and new bone formation, appear to be able to delay but not halt the progression of this condition. As a consequence of femoral head osteonecrosis, many individuals undergo surgical treatments including: core decompression, osteotomy, non-vascularized bone matrix grafting, free vascularized fibular grafts, limited femoral resurfacing, total hip resurfacing, and total hip arthroplasty.
Synthetic retinoid Am80 inhibits interaction of KLF5 with RARα through inducing KLF5 dephosphorylation mediated by the PI3K/Akt signaling in vascular smooth muscle cells
Authors: Zhang Xin-hua , Zheng Bin , Han Mei , Miao Sui-bing , Wen Jin-kun
Published: March 2009

MINT‐7013243: Klf5 (uniprotkb:Q66HP1) physically interacts (MI:0218) with RAR alpha (uniprotkb:Q9QWJ1) by anti bait coimmunoprecipitation (MI:0006)
Late Pleistocene sea-level oscillations (MIS 10–2) recorded in shallow marine and coastal plain sediments of the southern Wanganui Basin, New Zealand
Authors: Hughes Glenn R. , Kennedy David M.
Published: March 2009

The northern Wanganui Basin, New Zealand, is one of the key global sites for understanding marine cyclic sedimentation during the Quaternary. This paper presents the first evidence of marine cyclic sedimentation from its central-southern parts. Sedimentological, micropalaeontological and palynological analyses on a 280-m-deep borehole encountered units dating back to MIS 10. The sequence includes four marine cycles spanning MIS 9–5, which are overlain by terrestrial fluvial aggradation surfaces dating from MIS 4–2. Each marine unit represents a progressively shallowing depositional environment from the mid-shelf to coastal plain. This is overlain by a terrestrial sequence of lowstand fluvial terraces. Localized fault movements appear to have influenced the sedimentary character of the sequence during MIS 7a and 5e producing basement highs which provided protection to the shoreline. The cyclothems described in this paper now extend the already extensive, previously described record from MIS 17–10 to produce a combined eustatic record of Quaternary sea level change within the basin to MIS 5. They also provide an excellent example of the sedimentary response of a coastal basin to a progressive loss of sedimentation accommodation space.
Stationary waves at the interface between a plasma stream and magnetic field
Authors: Shivamoggi Bhimsen K.
Published: March 2009

A uniformly-streaming compressible and infinitely-conducting plasma is confined by a magnetic field aligned with the stream. The system is disturbed by introducing magnetic dipoles into the field. A Fourier-transform method is used to determine the displacement of the interface between the streaming plasma and the magnetic field within the framework of a ‘shallow-water’ approximation. For the case of a subsonic plasma stream, stationary waves appear on the interface upstream of the dipoles, and it is found that (i) these stationary waves are possible only if the gravity effects on the plasma are weak enough; (ii) the effect of surface tension at the interface is to reduce the amplitude and increase the wavelength of these waves. For the case of a supersonic plasma stream, however, stationary waves at the interface are not possible.
Filamentation and collapse of Langmuir waves in a weak magnetic field
Authors: Rolland P. , Tagare S. G.
Published: March 2009

The filamentation and collapse of Langmuir waves in a weak magnetic field are analysed in two particular cases of low-frequency acoustic perturbations: (i) adiabatic perturbations which correspond to subsonic collapse, and (ii) nonadiabatic perturbations which correspond to supersonic collapse. Here the existence of Langmuir filaments and Langmuir collapse in a weak magnetic field are due to nonlinear interaction of high-frequency Langmuir waves (which make small angle with the external magnetic field) with low-frequency acoustic perturbations along the magnetic field.
Alfvén soliton in a low-beta plasma
Authors: Shukla P. K. , Rahman H. U. , Sharma R. P.
Published: March 2009

An exact nonlinear Alfvén wave in a low-β plasma is investigated. Super Alfvén solitons with a density depression are found to exist. The analytical result for the small-amplitude soliton is given.
Anomalous transport coefficients in a magnetized turbulent plasma
Authors: Xiaoming Qiu , Balescu R.
Published: March 2009

In this paper we generalize the formalism developed by Balescu and Paiva-Veretennicoff, valid for any kind of weak turbulence, for the determination of all the transport coefficients of an unmagnetized turbulent plasma, to the case of a magnetized one, and suggest a technique to avoid finding the inverse of the turbulent collision operator. The implicit plasmadynamical equations of a two-fluid plasma are presented by means of plasmadynamical variables. The anomalous transport coefficients appear in their natural places in these equations. It is shown that the necessary number of transport coefficients for describing macroscopically the magnetized turbulent plasma does not exceed the number for the unmagnetized one. The typical turbulent and gyromotion terms, representing dissipative effects peculiar to the magnetized system, which contribute to the frequency-dependent transport coefficients are clearly exhibited.
Nonlinear wave interactions in a collisionless space and time dependent warm fluid plasma
Authors: Larsson Jonas
Published: March 2009

Expressions for the current response operators of first and second order are calculated for a fluid plasma with isotropic pressure terms. The unperturbed state is an arbitrary space and time dependent solution of the basic equations. The response operators are given in a form which shows explicitly the mathematical structure behind the approximate conservation of wave energy in resonant wave interactions. The coefficients in the coupled mode equations are expressed in terms of these response operators.
The mean electromotive force generated by random hydromagnetic waves in a collisionless plasma
Authors: Namikawa Tomikazu , Hamabata Hiromitsu , Hosoya Yasusi
Published: March 2009

The mean electromotive force generated by random hydromagnetic waves is calculated by using Fourier analysis methods for the cases of an incompressible Hall plasma and a compressible plasma with finiteβ. It is shown that in the case of a Hall plasma theαeffect can exist in the interaction between two waves which propagate in opposite directions and have different phase velocities and several newβ–terms are produced by the Hall effect, while in the case of a compressible plasma theα–effect can exist only in the interaction between the Alfvén mode and the fast or slow magneto-acoustic mode, and not between the fast and slow magneto-acoustic modes. The results are discussed in the context of the substorms in the earth's magnetosphere.
The mean electromotive force generated by random Alfvén waves in a collisionless non-uniform plasma
Authors: Hamabata Hiromitsu , Namikawa Tomikazu , Hosoya Yasusi
Published: March 2009

The mean electromotive force produced by random hydromagnetic waves in a collisionless plasma is investigated taking into account non-uniformities in the mean magnetic field, fluid velocity and plasma density. It is shown that the mean electromotive force associated with gradients in mean quantities and the helicity spectrum function of the random velocity field exists and has a component parallel to the mean magnetic field which is associated with field-aligned gradients in mean quantities and density gradients parallel to the mean flow. The results are discussed in the context of the field-aligned currents in the earth's magnetosphere.
Stability of solitary wave solutions of simultaneous nonlinear Schrödinger equations
Authors: Bhakta J. C. , Gupta M. R.
Published: March 2009

The stability of localized solitary wave solutions of simultaneous nonlinear Schrödinger equations describing different types of interacting waves in a plasma has been investigated. It is found that the stability depends on the nature and strength of the interaction potential between the two waves. The possible results of interactions between two colliding solitary waves have been discussed using the conservation laws.
Evolution of nonlinear Alfvén waves propagating along the magnetic field in a collisionless plasma
Authors: Khanna M. , Rajaram R.
Published: March 2009

It is shown that the asymptotic evolution of a finite-amplitude Alfvén wave propagating parallel to the uniform magnetic field in a warm homogeneous collisionless plasma is governed by the modified nonlinear Schrödinger equation. The dispersion is provided by the ion finite Larmor radius (FLR) effects in the momentum equation and the Hall current and electron pressure corrections to the generalized Ohm's law. In the cold plasma limit the equations reduce to those available in the literature. It is suggested that these calculations can have a bearing on the investigation of the structure of MHD waves in the solar wind.
Stochasticity in plasmas with electromagnetic waves
Authors: Mendonça J. T. , Doveil F.
Published: March 2009

The interaction of an electron with two electromagnetic waves propagating in an isotropic plasma is studied. It is shown, by numerical calculations, that the electron behaves stochastically, above a given threshold of the wave field amplitudes. The numerical threshold is compared with those given by analytical criteria. The results might be relevant to the laser-plasma interaction problem.
Electromagnetic cyclotron-loss-cone instability associated with weakly relativistic electrons
Authors: Wong H. K. , Wu C. S. , Ke F. J. , Schneider R. S. , Ziebell L. F.
Published: March 2009

The amplification of fast extraordinary mode waves with frequencies very close to the electron cyclotron frequency is investigated for a plasma which consists of a weakly relativistic electron component with a loss-cone type distribution and a cold background electron component. The basic mechanism of the amplification is attributed to a relativistic cyclotron resonance between the wave and the energetic electrons. The method employed in the present analysis enables us to solve the dispersion relation in a self-consistent manner for arbitrary ratio of the densities of the energetic and background electrons. It is found that the maximum growth rates occur at certain values of ω2pe/Ω2e and the angular dependence of the growth rate is sensitive to the ratios ω2pe/Ω2e and ne/nb. Here ωpe and Ωe are the electron plasma frequency and the electron cyclotron frequency, respectively, and ne and nb denote the number densities of the energetic and background electrons, respectively.
Collisionless electrostatic interchange instabilities
Authors: Gary S. Peter , Thomsen Michelle F.
Published: March 2009

The linear Vlasov dispersion equation for electrostatic plasma instabilities driven by gravity and weak density gradients perpendicular to a uniform magnetic field is derived and solved numerically. Two interchange instabilities emerge: the well-known fluid mode at long wavelengths and a kinetic mode at wavelengths short compared with the ion gyroradius. The properties of both instabilities are studied, as well as the effects of gravity on the universal and lower-hybrid density drift instabilities. The results show that the kinetic interchange generally has a larger growth rate than the fluid interchange instability, indicating that, whenever the latter is present in a collisionless plasma, the former may also be found.
Distortion of the distribution function of weakly RF heated minority ions in a tokamak plasma
Authors: Anderson D.
Published: March 2009

An investigation is made of the effect of RF-induced velocity diffusion on the distribution function, f(v), of the heated ion species in minority heating schemes using the fast Alfvén wave. The solution for the distorted distribution function is expressed in a Legendre series from which deviations from isotropy can be assessed. Solutions are found in the limits of high and low velocities and the elongation of the constant f(v) surfaces is also given.
Anisotropy in MHD turbulence due to a mean magnetic field
Authors: Shebalin John V. , Matthaeus William H. , Montgomery David
Published: March 2009

The development of anisotropy in an initially isotropie spectrum is studied numerically for two-dimensional magnetohydrodynamic turbulence. The anisotropy develops through the combined effects of an externally imposed d.c. magnetic field and viscous and resistive dissipation at high wavenumbers. The effect is most pronounced at high mechanical and magnetic Reynolds numbers. The anisotropy is greater at the higher wavenumbers.
Plasma transport in stochastic magnetic fields. Part 3. Kinetics of test particle diffusion
Authors: Krommes John A. , Oberman Carl , Kleva Robert G.
Published: March 2009

A discussion is given of test particle transport in the presence of specified stochastic magnetic fields, with particular emphasis on the collisional limit. Certain paradoxes and inconsistencies in the literature regarding the form of the scaling laws are resolved by carefully distinguishing a number of physically distinct correlation lengths, and thus identifying several collisional subregimes. The common procedure of averaging the conventional fluid equations over the statistics of a random field is shown to fail in some important cases because of breakdown of the Chapman-Enskog ordering in the presence of a stochastic field component with short autocorrelation length. A modified perturbation theory is introduced which leads to a Kubo-like formula valid in all collisional regimes. The direct-interaction approximation is shown to fail in the interesting limit in which the orbit exponentiation length LK appears explicitly. A higher-order renormalized kinetic theory in which LK appears naturally is discussed and used to rederive more systematically the results of the heuristic scaling arguments.
Linear density drift instabilities in very low beta plasmas: a different approach
Authors: Gary S. Peter
Published: March 2009

This paper reports a study of the linear Vlasov electromagnetic dispersion equation for density drift instabilities in very low β plasmas. A uniform magnetic field and a weak uniform density gradient are assumed. This paper differs from most other studies of this topic in three important ways: (i) no low-frequency or long-wavelength approximations are made, (ii) no gauge condition is imposed and (iii) a modification of the local approximation is used which is argued to be less arbitrary than the usual local approximation. Numerical solution of the resulting dispersion equation yields stabilization of the universal density drift instability at values of β somewhat higher than those obtained from the local approximation, and near maximum growth shows no evidence of coupling between the universal and Alfvén modes.
Effect of finite spectral width on the modulational instability of Langmuir waves
Authors: Bhakta J. C. , Majumder D.
Published: March 2009

The effect of finite spectral width on the modulational instability of Langmuir waves has been investigated applying a method developed by Alber to derive a transport equation for the spectral density. The numerical results presented show that the spectrum is stable against modulational perturbation when the spectral width exceeds some critical value. For a Gaussian spectrum, the maximum growth rate is less than that for a monochromatic wave but the domain of modulational instability is extended. For a uniform distribution the shift in the growth rate curve towards the region of shorter wavelength is more pronounced and, for a certain range of spectral width, the maximum growth rate exceeds that for a monochromatic wave.
On the negative resistance of double layers
Authors: Raadu M. A. , Silevitch M. B.
Published: March 2009

The negative resistance of double layers has been invoked to explain instability in diode currents, and the flickering aurora phenomenon. In this paper the theory of the negative resistance is extended by a more detailed account of the constraints that are imposed on the electron distributions in the double layer. Attention is concentrated on the energetic trapped electrons which originate at the high potential side of a double layer.
Large-amplitude disturbances caused by ion-rich sheath motion
Authors: Coates A. J. , Edgley P. D. , Allen J. E.
Published: March 2009

We present the first detailed experimental study of the plasma response to movement of a plane ion-rich sheath. The results show clearly that ion rarefaction waves are associated with sheath expansion while ion enhancement (‘compressive’) waves are formed on sheath collapse. The data are compared successfully with a nonlinear theory which includes the presence of a presheath prior to the sheath motion.
Improved derivation of the modified BGK collision term and applications to the Hall effect and cold plasma dispersion relation
Authors: Nagata M.
Published: March 2009

We improve our previously derived addition to the BGK collision term, and express it in a simple form. The collision frequency for scattering now depends anisotropically on the velocity vector. We also apply the improved macroscopic equation of momentum flow to the Hall effect, the cold plasma dispersion relation and the cyclotron resonance. The Hall coefficient which is constant in the case of the BGK collision term now depends on the magnetic field. It is also shown that, compared with the almost symmetric classical curves of cyclotron resonance, the new curves are considerably asymmetric and their half-widths are about 3/2 times the classical ones.
Corrigendum and Addendum
Authors: Shivamoggi Bhimsen K.
Published: March 2009

The following are corrected versions of the equations (in the original numbering):

In (75) and the subsequent expressions, ⅜ should replace the number ⅝. Thus (80) should be

These corrections affect the results in the paper only in detail and the conclusions therein remain unchanged.
Propagation of hydromagnetic waves in a cold plasma mixed with hot electrons
Authors: Hamabata Hiromitsu , Namikawa Tomikazu
Published: March 2009

The propagation of small-amplitude hydromagnetic waves in a cold plasma mixed with hot electrons is investigated using the first order CGL equations for electrons. It is assumed that in an equilibrium state the electrons consist of two components, cold electrons and hot electrons with bi-Maxwellians. Propagation properties of hydromagnetic waves are analysed by use of phase speed and refractive index surfaces, polarization, and the amplitude ratio between perturbed density and magnetic field. It is shown that the existence of cold electrons affects the properties of hydromagnetic waves through finite frequency corrections only when the temperature anisotropy exists; and that the existence of cold electrons diminishes the resonance angle and the critical angle at which the polarization sense changes from left-handed to right-handed, and also weakens the tendency of intermediate waves to follow the lines of force of the static magnetic field.
Magnetohydrodynamic plasma instability driven by Alfvén waves excited by cosmic rays
Authors: McKenzie J. F. , Webb G. M.
Published: March 2009

Hydrodynamical equations describing the mutual interaction of cosmic rays, thermal plasma, magnetic field and Alfvén waves scattering the cosmic rays used in cosmic ray shock acceleration theory (e.g. McKenzie & Völk 1982; Drury 1983; Webb 1983) are analysed for long-wavelength linear compressive instabilities. The Alfvén wave field may contain a pre-existing component as well as a component excited by the cosmic ray streaming instability. In the case of no Alfvén wave damping, adiabatic wave growth and Alfvén wave generation by the cosmic ray streaming instability, it is found that the backward propagating slow magneto-acoustic mode is driven convectively unstable by the pressure of the self-excited Alfvén waves, provided the thermal plasmaβis sufficiently large. The equations are also analysed for the case where the Alfvén wave growth is balanced by some nonlinear damping mechanisms. In the latter case both the forward and backward propagating slow magneto-acoustic modes may be driven unstable if the plasmaβis sufficiently small. The conditions under which the instabilities occur are delineated, and sample calculations of growth rates given. Possible applications of the instabilities to astrophysical situations are briefly discussed.
A note on Lindhard's representation for transverse and longitudinal dielectric constants
Authors: Frood D. G. , Scaife B. K. P.
Published: March 2009

Lindhard's relation between the transverse and longitudinal permittivities and the magnetic susceptibility is shown to be incorrect. The tensorial nature of the wave-vector- and frequency-dependent dielectric permittivity is emphasized. A Vlasov plasma is used as an illustrative counter-example.
High-energy kinetic theory of a particle beam generated plasma
Authors: Peyraud N.
Published: March 2009

The equilibrium high-energy electron distribution in a particle beam generated plasma is calculated. The tail of the distribution, above the first excited state, is derived from a Boltzmann equation which contains inelastic collisional processes and a continuous source term. This equation is analytically solved by a Laplace transformation method and, in a numerical application for the case of an argon plasma created by a high-energy electron beam between 103 and 106eV, the branching ratios for energy deposition in ionization and excitation states are calculated. We compare the results with those of the laser group of Orsay.
Cyclotron radiation from a relativistic electron beam in a static magnetic field
Authors: An Z. G. , Lee Y. C. , Lee T. T. , Chen H. H.
Published: March 2009

Electromagnetic cyclotron instabilities of a relativistic electron beam propagating in an external magnetic field are studied by considering electron motion inside a self-consistent electromagnetic field. When the number of electrons in a subgroup is greater than two, or when the phases are random, the linear dispersion relation obtained agrees with that of Chu et al. for a gyrotron in a ring model. When the number of electrons in a subgroup is limited to two only, the linear dispersion relation is different in that it has an instability threshold. Completely nonlinear motion is also studied using the method of Poincaré's return map, or by considering the departure rate of nearby trajectories. Stochasticity is observed in the nonlinear oscillation of the wave-particle system when a critical energy is exceeded. Physical implications for gyrotron operation are also discussed.
Unified kinetic theory of plasma correlations
Authors: Guillen Michael A. , Liboff Richard L.
Published: March 2009

A unified approach to the kinetic theory of correlations in a plasma is presented, based on the BBKGY hierarchy. The theory is applied to a one-component plasma with the Coulomb interaction modified to include effects of the background. Closed integro-differential equations in space, momentum and time are obtained for the two-particle correlation function in both the strong and weak coupling limits. To corroborate the theory, the formalism is applied in the equilibrium limit. In the weak-coupling domain, γ ≪ 1, the time-independent analysis returns the well-known linearized Debye-Hückel result, where γ is the plasma parameter. In the strong-coupling domain with γ ≥ 1, the resulting two-particle ‘total’ correlation function exhibits decaying oscillatory behaviour for particle separation of the order of the effective interparticle range. Exponential behaviour of the correlation function found for small values of particle separation agrees with previous results of statistical mechanics.
Toroidal plasma configuration with non-planar magnetic axis
Authors: Rizk Hussain M.
Published: March 2009

The ideal MHD equilibrium, stability, classical diffusion, effective thermal conductivity, and Ohmic heating of a zero-shear toroidal plasma configuration with a single non-planar magnetic axis of variable torsion and curvature are investigated. The plasma has a circular cross-section through which a longitudinal current density with arbitrary profile flows. In this type of magnetic configuration, the magnetic surfaces arbitrarily rotate around the magnetic axis. This magnetic toroidal configuration is of a stellarator type with a non-planar magnetic axis. The present work also covers as special cases tokamak and a magnetic toroidal plasma configuration with a magnetic axis of arbitrarily modulated curvature.
Stability theorem for KdV-type equations
Authors: Laedke E. W. , Spatschek K. H.
Published: March 2009

A general KdV-type equation which covers most of the known model equations for weakly dispersive waves is investigated. First, the possible stationary localized states are discussed. When perturbed longitudinally, the perturbations can be finite and complex but should be small. In the main (second) part of the paper a necessary and sufficient stability criterion for the stationary states is derived. This is performed in two steps: A variational formulation leads to an instability region, whereas the sufficient stability criterion follows from a Liapunov functional. The stability theorem is evaluated for various models including ion-acoustic waves in plasmas and lower-hybrid cones.
Kinetic theory of electromagnetic instabilities in weakly ionized neon plasma with inelastic collisions
Authors: Žigman V. J. , Milić B. S.
Published: March 2009

The spectra and the instability criteria for the two electromagnetic wave modes previously found to exist in weakly ionized plasmas placed in an external d.c. electric field are analysed here for neon plasma for a wide range of the parameter Eo/nn. The presence of electron-atom inelastic collisions is taken into account, assuming that the electron temperature is in the range where these collisions dominantly result in atomic excitations. The linearized kinetic equations are used in combination with a previously evaluated non-Maxwellian electron steady-state distribution function appropriate for the situation in which collisional excitations are significant. For any given ratio of electron drift to thermal velocity, the wavelengths and the angles of propagation at which the instabilities are predicted to set in are determined.
Dispersion surfaces
Authors: André Mats
Published: March 2009

The dispersion relation of linear waves in a non-relativistic, collisionless and homogeneous magnetized plasma is solved by numerical methods. Both electrostatic and electromagnetic waves with frequencies from below the ion gyrofrequency to above the electron gyrofrequency are studied for all angles of propagation. Modes occurring in a cold plasma as well as waves dependent on thermal effects are included. Dispersion surfaces, that is plots of frequency versus wave vector components, are presented for some plasma models. This presentation shows all interesting waves clearly and reveals how different modes are related. The dispersion surfaces can be used as an aid, for example, when comparing wave observations and theory, and they may also help to avoid confusing nomenclature.
On the self-modulation of whistler waves propagating along the external magnetic field
Authors: Mann G.
Published: March 2009

This paper deals with the evolution of a small initial perturbation superimposed on a plane whistler wave due to self-modulation in the case of propagation along the external magnetic field.
Period doubling of azimuthal oscillations on a non-neutral magnetized electron column
Authors: Boswell R. W. , Giles M. J.
Published: March 2009

We investigate the low-frequency azimuthal oscillations on a non-neutral magnetized electron column of very low density. A perturbation analysis of the slow mode of the rigid rotator equilibrium is developed to illustrate the nature of large-amplitude fundamental-mode oscillations. The results of this theoretical analysis show two important characteristics: firstly, as the perturbation amplitude is increased the wave form ceases to be purely sinusoidal and shows period doubling. Secondly, above a certain threshold, all harmonics of the wave grow and the wave breaks. The results of the former are compared with a simple electron beam experiment and are found to be in good qualitative agreement.
Switched-on evolution due to a temporal electron charge drifting subthermally through a warm collisional plasma
Authors: Chee-Seng Lim
Published: March 2009

An electron charge is suddenly switched on while drifting through a warm collisional plasma. It acts thereafter with an arbitrary time-dependence. The evolution of the plasma, initially at rest, is considered in two and three dimensions. A general solution is first established for drift-modified slow plasma modes and then employed in subthermal drift analysis. Its abrupt switch-on causes the electron charge to release, during subthermal drift, a fully symmetric thermal front Г which subsequently expands ahead of it into an undisturbed receding expanse. A transversely symmetric response develops inside Г. On switch-off, the drifting charge releases another thermal front Г0which also precedes it but trails non-concentrically behind Г. Plasma response continues after switch-off. Response properties between Г and Г0differ strikingly from those inside Г0. Applications are next considered, first in three dimensions, for a subthermal pulsating electron with a generally complex frequencyω. The prepermanent state response inside Г comprises an axisymmetric dominant componentø∞plus a spherically symmetric transient componentøtr.ø∞acquires the frequencyω.øtrhas amplitudes dependent on and wave crests independent of both frequencyωand drift; it suffers a fast (slow)ω–independent temporal attenuation in a collisional (collisionless) plasma. The geometrical drift wave structure ofø∞is closely examined for realωand a collisionless plasma. Every energy surface associated withø∞nucleates at the electron; from there, it evolves slower than a phase surface, which eventually ‘disappears’ past Г. The leading energy surface, which nucleated at switch-on, develops permanently inside Г; it serves as an energy front that seals off the energy sustainingø∞since switch-on. Finally, the two-dimensional evolving drift field of an activated antenna line is computed.
Self-focusing of nonlinear ion-acoustic waves and solitons in magnetized plasmas
Authors: Infeld E.
Published: March 2009

The Zakharov-Kuznetsov equation describing Korteweg–de Vries waves and solitons in a strong, uniform magnetic field is rederived taking space stretching to be isotropic. This equation is then used to investigate nonlinear waves and solitons for long-wave instabilities. A solid angle of instability develops around the plane perpendicular to the magnetic field. For weakly nonlinear waves this angle is very narrow: widening as the amplitude of the nonlinear wave is increased. The soliton wave is unstable for all directions other than parallel to the field. Previous results of other authors, limited to solitons and perpendicular propagation are recovered. Calculations are illustrated by polar diagrams for the perturbations. Some broader implications are pointed out.
The general Lie group and similarity solutions for the one-dimensional Vlasov–Maxwell equations
Authors: Roberts Dana
Published: March 2009

The general Lie point transformation group and the associated reduced differential equations and similarity forms for the solutions are derived here for the coupled (nonlinear) Vlasov–Maxwell equations in one spatial dimension. The case of one species in a background is shown to admit a larger group than the multi-species case. Previous exact solutions are shown to be special cases of the above solutions, and many of the new solutions are found to constrain the form of the distribution function much more than, for example, the BGK solutions do. The individual generators of the Lie group are used to find the possible subgroups. Finally, a simple physical argument is given to show that the asymptotic solution (t→∞) for a one-species, one-dimensional plasma is one of the general similarity solutions.
Experiments on ion-acoustic rarefactive solitons in a multi-component plasma with negative ions
Authors: Nakamura Y. , Ferreira J. L. , Ludwig G. O.
Published: March 2009

Ion-acoustic solitons in a three-component plasma which consists of electrons and positive and negative ions have been investigated experimentally. When the concentration of negative ions is smaller than a certain value, positive or compressive solitons are observed. At the critical concentration, a broad pulse of small but finite amplitude propagates without changing its shape. When the concentration is larger than this value, negative or rarefactive solitons are excited. The velocity and the width of these solitons are measured and compared with predictions of the Korteweg-de Vries equation which takes the negative ions and the ion temperature into consideration. Head-on and overtaking collisions of the rarefactive solitons have been observed to show that the solitons are not affected by these collisions.
RF current drive with magnetic helicity injection
Authors: Bhadra D. K. , Chu C.
Published: March 2009

External injection of magnetic helicity into a plasma may be possible through the introduction of appropriately polarized electromagnetic waves. A concept of steady-state current-drive is presented, based on the validity of conservation of helicity (appropriately defined for finite frequency processes). It is shown that such external injection of helicity can maintain a steady-state current by compensating the volt-seconds consumed through plasma resistivity. Such a mechanism, if experimentally successful, is particularly interesting at high densities because the efficiency of the process does not depend on plasma density, as opposed to other radio-frequency current-drive techniques.
Instability of low-frequency waves in a cold plasma mixed with hot electrons
Authors: Hamabata Hiromitsu , Namikawa Tomikazu
Published: March 2009

The instability of low-frequency waves in a cold plasma mixed with hot electrons is investigated using the first-order CGL equations for electrons. It is assumed that in an equilibrium state the electrons consist of two components, cold electrons and hot electrons with bi-Maxwellians. It is shown that low-frequency waves with right-hand polarization can be generated by the hot electron temperature anisotropy and the existence of cold electrons.
An average Lagrangian formulation of ponderomotive forces in Vlasov plasmas
Authors: Kentwell G. W.
Published: March 2009

Whitham's averaged Lagrangian principle, and the Low Lagrangian are used to derive the averaged Lagrangian for slowly varying electrostatic and electromagnetic wave packets in dispersive Vlasov plasmas. From the averaged Lagrangian, the stress tensor and wave-momentum densities are derived for the total wave-particle system. For a specific division of these total quantities into wave and background parts, time-dependent ponderomotive forces in Vlasov plasmas are derived from a momentum conservation theorem. We also show that the wave-induced magnetization current can be derived by the averaged Lagrangian method.
Ion-acoustic instabilities driven by an ion velocity ring
Authors: Akimoto K. , Papadopoulos K. , Winske D.
Published: March 2009

A ring distribution of ions in velocity space can generate electrostatic waves which propagate predominantly along an ambient magnetic field at frequencies comparable with the ion plasma frequency. A dispersion equation which accounts for these waves is presented, and solved analytically and numerically. It was found that ion-acoustic-like waves are excited in a plasma even if the electron temperature is comparable with the ion temperature under the assumption of an anisotropic ion distribution.
Cerenkov and cyclotron instabilities in a plasma stream
Authors: Knox C. F.
Published: March 2009

The model of a stationary medium traversed by a weak plasma stream directed along a magnetic field is investigated. The usual linear treatment is adopted, and the stream is taken to be ‘cold’, with only electron (perturbation) motions considered. The objective is to assess the plane-wave growth associated with both Cerenkov and cyclotron instabilities; in particular, the dependence of the growth on frequency and angle of phase propagation. The main discussion is of the case when the stationary medium is a cold plasma in which both electron and positive ion motions are taken into account. Various expressions for the growth are derived, and numerical calculations are presented in graphical form.
Dispersion of the whistler mode for a velocity distribution with a loss cone
Authors: Das A. C.
Published: March 2009

Considering the general dispersion equation for the whistler mode, the condition of critical stability is discussed and the values of k2 and the field strength for critical stability are determined. The waves grow due to resonance; the stability criterion is studied and the growth rate is also calculated. The results for a special case of simple velocity distribution with a loss cone are obtained and compared with those due to cold dispersion. In the magnetosphere the thermal electrons which can be treated as cold, should be included in the distribution and this is discussed in § 5. Finally, we have established the regions of stable and unstable plasma for the special velocity distribution function and it can be seen how these depend on the size of loss cone.
The respone of a spherical plasma probe to alternating potentials: Results of computations and use for plasma diagnostics
Authors: Buckley R.
Published: March 2009

In a previous paper, the R.F. characteristics of a spherical probe immersed in a hot, low-density plasma using a realistic sheath model were considered, and a few results of computations presented. The remainder of these results are given in this paper. The dependences of R.F. admittance, and rectified current on probe radius, d.c. bias, and electron neutral collision frequency are exhibited and shown to be qualitatively in accord with the predictions of simple slab-sheath/dielectric models. It is shown how in principle, analysis of resonance rectification characteristics using curves included in the paper can yield values of electron densitynetemperatureTe, and electron-neutral collision frequency ν. Two methods of reduction are applied to some laboratory results obtained at Slough and are shown to give reasonably consistent values ofneand ν, but the values ofTe, show considerable scatter. These methods could complement the Langmuir probe which gives more reliable values ofTethan ofnein low density plasmas withne≾108cm−3. Effects of magnetic fields are not included in this paper.