bluuebunny/crossref_metadata_2025 huggingface dataset:
The Potsdam image processing software
Authors: Böhm P.
Published: July 2007

The method of adaptive filtering as a useful tool for the smoothing and analysing of astronomical images is described in a heuristic way. The filter recognizes the local signal resolution (which usually varies strongly across the image) and adapts its own impulse response to this resolution. The advantages of this method are explained and some examples are given.
Spectroscopy of Blue Compact Galaxies
Authors: Esposito A. A. M. , Rafanelli P. , Lipovetskid̊ V. A.
Published: July 2007

Blue Compact Galaxies (BCGs) are gas‐rich systems undergoing very massive starburst events which involve the entire galaxy. We performed a spectroscopic study of 12 BCG in order to determine metallicities and helium content. Some objects show presence of broadened emission lines, probably due to internal motion of the interstellar medium, caused by intense stellar winds and supernova explosions.
Spectroscopic analysis of the nuclear and circumnuclear regions of the Seyfert 2 galaxy NGC 7130
Authors: Radovich M. , Rafanelli P. , Birkle K. , Richter G. M.
Published: July 2007

We discuss here the spectroscopic properties of the Seyfert 2 galaxy NGC 7130 (= IC 5135). Emission line regions were isolated and line ratios were measured and fitted with photoionization models; this allowed to discriminate between thermal and non thermal ionization in the circumnuclear regions. Massive star formation is likely to occur at projected distances from the nucleus ≫ 2 kpc: line profiles in these regions suggest the presence of outflows of gas due to stellar winds from hot massive stars.
Galaxy activity and interaction: the optical view
Authors: Rafanelli P. , Temporin S. , Baruffolo A.
Published: July 2007

The relevance of interaction to the presence of Seyfert or starburst activity in the nuclei of galaxies is examined. We focus the attention on the close environments of spectroscopically selected samples of Seyfert‐1, Seyfert‐2 and starburst galaxies. In particular the results of a statistical procedure aimed at finding physical pairs are tested with redshift measurements of the identified pairs. Seyfert and starburts galaxies show an excess of physical companions compared to normal galaxies. This excess tends to increase as one moves from Seyfert to starburst galaxies.
Schmidt survey in the Galactic anticentre direction. 1. Investigation of open clusters
Authors: Kharchenko N. , Andruk V. , Schilbach E.
Published: July 2007

A study of four open clusters in the direction of the Galactic anticentre (l = 186°, b = +2°) is presented. In a field of 8.32 square degrees proper motions and B magnitudes for about 79 000 stars down to 19.5 were determined on Tautenburg Schmidt plates. For more than 15 500 of them U magnitudes down to 17.3 could be obtained. Additionally, OCA Schmidt plates were used to determine V, R magnitudes in a larger field of 24.45 square degrees for 271 000 stars down to V = 18.2. For stars brighter than V = 15.5 an accuracy of about 1.5 mas/yr has been estimated for proper motions. The rms errors of stellar magnitudes and colour indices are 0.09 – 0.12 mag.

Several open clusters have been already known in this direction of the sky, e.g. NGC 2168 or M 35 (C 0605+243), NGC 2158 (C 0604+241) and IC 2157 (C 0601+240). Inspecting the plates and analysing the colour‐magnitude diagrams and published data, we could identify an additional anonymous cluster C 0605+242 with a projection on the sky near the centre of M 35 but at a larger distance from the Sun.

The cluster membership determination was carried out using information on spatial and proper motion distributions of stars in the field. The colour‐magnitude diagrams were derived down to the limiting stellar magnitude. For each cluster the interstellar extinction Av, the diameters of the core and corona, the ages and spatial velocity components (V,W) relative to the LSR in the Y,Z – Galactic directions were determined.

The distances to the clusters of 960 pc, 2 600 pc, 2 520 pc and 3 700 pc were obtained for M 35, IC 2157, C 0605+242 and NGC 2158. They show the loci of the clusters in the Local and Perseus spiral arms and at external border of Perseus arm, respectively.
Are short‐time variations of the solar S‐component emission identical with microwave bursts?
Authors: Nefedev V. P. , Smolkov G. Ya. , Agalakov B. V. , Krüger A. , Hildebrandt J.
Published: July 2007

Extended time series (time resolution about 2–3 min) of spatially resolved observations (≫ 17 arcsec) in one dimension of solar S‐component sources obtained at the Siberian Solar Radio Telescope (SSRT) at 5.2 cm wavelength allow the detection of evolutional features of the growth and decay of active regions in the solar corona. Characteristic slow flux variations with timescales of about 1–2 hours occurring during the decay phase of the radio emission in the low corona above plages and sunspots are compared with recently detected step‐like flux increases on timescales of about 10–20 min followed by quasi‐constant periods appearing in the initial phase of the development of active regions. Superimposed on this basic behaviour, also fluctuations at shorter timescales (or even periodic oscillations) have been observed.

As it is well known from emission‐model calculations, the variations of the S‐component radiation can be due to variations of the magnetic field and/or changes of the energy of the radiating particles, which is basically the same emission mechanism as for microwave bursts. Since the “S‐component” is originally defined by its long timescale behaviour derived from whole‐Sun flux density measurements, the presently detected small‐timescale features in S‐component sources require either a revised definition of S‐component emission or must be considered as “burst‐like”.
Proper motions, absolute magnitudes and spatial distribution of Zirconium stars
Authors: Chanturiya S. M.
Published: July 2007

The computational algorithm to determine the the proper motions of Zirconium stars on the basis of catalogues “Carte du Ciel” and on the recent photographic observations carried out with the 70cm Abastumani meniscus telescope is presented. It allowed to determine the proper motions of 288 stars in the region around α Per with a rms error of ± 0,004 arcsec/yr. Applying the method proper motions of 74 Zirconium stars and 146 control stars have been obtained. The error of proper motions obtained for the North Zone (δ > −2°) 109 AGK3 control stars is ± 0.006 arcsec/yr.

On the basis of proper motins absolute magnitudes were separately calculated for the MCLPZS and LASZS.

For the MCLPZS the average absolute visual magnitude at maximum, corresponding to the mean period of P = 350 days, equals −3ϕm.9. For the LASZS the mean absolute visual magnitude, corresponding to the apparent median ones equals −1ϕm.9. Low luminosity (Mv = −1ϕmϕ9) Zirconium stars escape rather far (at a distance of up to 2 kpc) to the South from the Galactic plane into the region l ∼ 240 – 260°, where its assumed to be a connection with the Large Magellanic Cloud (LMC) begins to appear. Low luminosity Zirconium stars are weakly correlated with position of the Galaxy spiral arms. The MCLPZS show a somewhat other distribution.
The X‐ray background and the AGN X‐ray luminosity function
Authors: Hasinger G.
Published: July 2007

ROSAT deep and shallow surveys have provided an almost complete inventory of the constituents of the soft X‐ray background which led to a population synthesis model for the whole X‐ray background with interesting cosmological consequences. According to this model the X‐ray background is the “echo” of mass accretion onto supermassive black holes, integrated over cosmic time. A new determination of the soft X‐ray luminosity function of active galactic nuclei (AGN) is inconsistent with pure luminosity evolution. The comoving volume density of AGN at redshift 2–3 approaches that of local normal galaxies. This indicates that many larger galaxies contain black holes and it is likely that the bulk of the black holes was produced before most of the stars in the universe. However, only X‐ray surveys in the harder energy bands, where the maximum of the energy density of the X‐ray background resides, will provide the acid test of this picture.
Isolated neutron stars in the ROSAT Survey
Authors: Haberl F. , Motch C. , Pietsch W.
Published: July 2007

Two very promising candidates for isolated old neutron stars (IONS) accreting interstellar matter were found so far in ROSAT data. RXJ1856.5–3754 and RXJ0720.4–3125 are soft X‐ray sources with very similar X‐ray spectrum, long term temporal behaviour and faint optical counterpart. In addition RXJ0720.4–3125 shows 8.4 s pulsations which allow to constrain the magnetic field strength of the neutron star. We carried out a search for additional IONS with similar properties in the ROSAT all‐sky survey data of the galactic plane and present RXJ0806.4–4123 as further promising candidate.
Astronomische Nachrichten — Instructions for Authors Using LATEX Markup
Authors: Fritze K. , Schwope A. D.
Published: July 2007

This article gives instructions for authors of Astronomische Nachrichten (AN) how to prepare an article according to the current LATEX style. The source code of this paper may be used by the authors of AN as a template. For further information about the journal please look at the World Wide Web (URL http://www.aip.de:8080/∽astr_n/) where this text and accompanying style files can be obtained from.
BVRI photometry of possible standard stars in NGC 188
Authors: Kamél L.
Published: July 2007

CCD photometry of possible standard stars, in Cousins B, V, R and I, in a field in the region of NGC 188 is presented.
Mass distribution in the open cluster NGC 1664
Authors: Missana M. , Missana† N.
Published: July 2007

We start with the hypotheses that the cluster space is limited by an ellipsoid with a semiprincipal axis directed to the observer and that the star density inside of concentric ellipsodal layers remains constant, although varying from layer to layer. It results that the mean star mass at the periphery of the cluster is 0.59 Sun masses smaller than that at the center.
The shapes of Shakhbazian compact groups of galaxies
Authors: Oleak H. , Stoll D. , Tiersch H. , Macgillivray H. T.
Published: July 2007

We have completed an investigation (preliminary results for which were reported in Oleak et al. 1995) into the shapes of Shakhbazian compact groups of galaxies. Ellipticites for 299 groups in the Shakhbazian survey have been examined using the technique proposed by Rood (1979) for deriving the average “flatness” of a large sample of objects. The distribution of the apparent axial ratios (g = b/a) for the groups is found to be broad with a mean of< b/a > ∽ 0.5. This distribution is compared with randomly generated spherical and elliptical model systems. The results confirm the findings of our earlier study: the frequency distribution of axial ratios for Shakhbazian groups is represented soley by a population of prolate spheroids with low intrinsic axial ratios, < q > = 0.3, σ = ∽0.17 (assuming random true orientations in 3D space). This now provides further strong evidence that the Shakhbazian groups are more highly flattened than either rich clusters or elliptical galaxies, and represent the most elongated systems yet found. The result also provides confirmation of the reality of the groups, since in the case of systems of chance line‐of‐sight superpositions of galaxies we would expect to see much higher axial ratios.
Application of principal component analysis to radio properties of Quasars
Authors: Denis‐Karafistan A.
Published: July 2007

The principal component analysis method has been applied to two samples of nearby and distant quasars with well known radio data. Relationships between physical parameters pertinent to radio morphology has been searched and the significant number of dimensions of the manifold has been found to be two. The results of this analysis confirm the existence of a redshift luminosity correlation for a subset of 36 nearby, but to a lesser extent for 43 distant, quasars. An anticorrelation seems to exist between luminosity and linear sizes for the last sample. On the other hand, application of this analysis to the above samples indicates no correlation between the viewing angle and the other physical parameters.
A review of diagnostic emission line ratios in the Narrow Line Region of Active Galactic Nuclei
Authors: Radovich M. , Hasinger G. , Rafanelli P.
Published: July 2007

The availability of new observing facilities both from ground and space such as the Keck 10m telescope and the Hubble Space Telescope is casting new light on the spectroscopic investigation of emission line galaxies. In particular, it is now possible to detect spectra with a significantly improved signal to noise ratio in a very wide wavelength range, from the ultraviolet to the near infrared (HST, Keck) and beyond (ISO is unveiling the far infrared domain). As we move to high redshifts, however, it is more likely that the observed spectra are given by the contribution of different components in the galaxy: in particular, this may be the case if an Active Galactic Nucleus (AGN hereafter) emitting a power‐law continuum is surrounded by regions with strong star formation activity. The identification of the source which ionizes the line emitting regions is then complicated by the fact that we are observing the integrated spectrum from regions which are ionized by different sources. In this paper we wish to review which line ratios may be used in order to discriminate between photoionization by young stars and power‐law continuum in the wavelength range from 1200 Å to 100 μm. To this aim we used the photoionization code Cloudy (Ferland 1996) to present a series of diagnostic diagrams showing the dependence of emission line ratios on the main input parameters of photoionization models in the case of one component models with gaseous clouds ionized by (1) a stellar continuum typical of an HII region and (2) a power‐law continuum typical of an AGN: these line ratios are plotted as isoratio maps for different values of the hydrogen density, ionization parameter and slope of the power‐law continuum. We then show how the results may be affected by more realistic assumptions about the environment of the ionized gas: to this aim, we show the effects on selected line ratios of (a) the presence of two populations of clouds with different densities and (b) an AGN surrounded by regions with strong star formation activity.
On the completeness of the lists of Compact Galaxy Groups
Authors: Tovmassian H. M. , Cardena O. , Tiersch H.
Published: July 2007

It is shown that the lists of Shakhbazian Compact Galaxy Groups (SCGGs) are not complete. The number of the detected groups in the strip between b = ±30° and b = ±20° is by four to five times smaller than expected. The most probable reason is that during the search for SCGGs it was hard to distinguish images of compact galaxies from that of stars on the POSS prints in dense areas of the sky at lower galactic latitudes. There is some deficit of the detected groups between 60° and 40° of the north galactic latitudes. The surface density of SCGGs in the southern galactic hemisphere between b = −50° and b = −30° is by about three times less than it is expected. Obviously, the southern sky has not been searched properly. The list of Hickson's groups is complete down to galactic latitude ±30°. However, some excess of HCGs is found in the southern hemisphere, where the surface density of the found groups is by about two times higher than that of in the northern hemisphere.
The luminosity index for M stars and the distance to the LMC
Authors: Schmidt‐Kaler TH. , Oestreicher M. O.
Published: July 2007

On the bases of the new classification system introduced by Malyuto et al. (1997) a new technique to determine luminosities for M type stars has been established. Due to the lack of accurate distances and their inhomogeneity especially for supergiants the intrinsic scatter is rather high with 0.4 to 0.5 mag. The uncertainty of the zeropoint is 0.07 to 0.08 mag.

Applying our new method to M supergiant members of the LMC a distance modulus of 18.34 ± 0.09 mag is derived which agrees well with recent work. The luminosities of the stars range from those of galactic Iab to those of Ia‐Ia‐0 supergiants, i.e. the upper luminosity limit does not exceed that of their galactic counterparts.

Like the CaII H and K emission technique of Wilson & Bappu (1957), for which a revised calibration is given, the new method spans an extremely wide range of luminosities. It is less universal, as it can be applied to M stars only, but not to K stars. On the other hand the Wilson‐Bappu‐method requires high resolution spectroscopy so that it is restricted to bright stars in our Galaxy. Our new technique may be applied to faint stars in nearby galaxies since it requires low resolution spectroscopy only.
Hydromagnetic stability analysis of a Solar prominence suspended in an external horizontal magnetic field
Authors: GalindoTrejo J.
Published: July 2007

Among the observed characteristics of quiescent solar prominences, stability is perhaps the most important requirement for theoretical models of these coronal structures. Only stable equilibria can explain the presence of such cool and dense plasma sheets for extended periods of time. Utilizing the MHD‐Energy Principle (Bernstein et al. 1958) we investigate the linear stability properties of the two‐dimensional prominence equilibrium of Osherovich (1985). Incorporating a finite magnetic energy and a continous magnetic field, this model takes into account explicitly an external horizontal magnetic field in which the prominence is suspended. The presented numerical calculations indicate that the prominence model of Osherovich is stable and can explain the main features of reported oscillations. Instabilities occur only when model parameters are unrealistic for physical conditions in solar prominences.
N‐ Versus P‐Coordination in Bis(amino)cyclodiphosph(III)azane Complexes of Aluminum
Authors: Rastätter Marcus , Roesky Peter W. , Gudat Dietrich , Deacon Glen B. , Junk Peter C.
Published: July 2007

The reaction of the bis(amino)cyclodiphosph(III)azane, cis‐{(tBuNH)2(PNtBu)2}, with AlMe3, AlClMe2, AlCl2Me, and AlCl3 is reported. The less Lewis acidic compound AlMe3 forms the adduct cis‐[(tBuNH)2(PNtBu){P(⋅AlMe3)NtBu}] (1), in which the aluminum atom is exclusively coordinated to one phosphorus atom. At elevated temperatures AlMe3 undergoes migratory exchange between the two phosphorus atoms, but no methane elimination is observed. By using the more Lewis acidic compound AlClMe2 the P‐coordinated compound cis‐[(tBuNH)2(PNtBu){P(⋅AlClMe2)NtBu}] (2) can be obtained at low temperatures. Compound 2 rearranges irreversibly to a product in which the AlClMe2 group is coordinated by one exo‐cyclic nitrogen atom. A concomitant 1,2‐H shift from this nitrogen atom onto the phosphorus atom is observed. The N‐coordinated rearrangement product slowly decomposes via a PN bond cleavage in solution. Reaction of the even more Lewis acidic compounds AlCl2Me and AlCl3 finally led to stable adducts, cis‐[(tBuNH)(PNtBu)(tBuN⋅AlCl2Me){P(H)NtBu}] (3), and cis‐[(tBuNH)(PNtBu)(tBuN⋅AlCl3){P(H)NtBu}] (4), in which the aluminum atoms are N‐coordinated by a tBuNPH unit.
Alternative Validation of a LC‐MS/MS‐Multi‐Method for Pesticides in Drinking Water
Authors: Müller Alexander , Flottmann Dirk , Schulz Wolfgang , Seitz Wolfram , Weber Walter H.
Published: July 2007

The development of instrumental analytics such as the LC‐MS/MS has made it possible to quickly determine many component concentrations in a single chromatogram. However, the validation of such multi‐methods needs new strategies for robustness and optimization. Statistical execution of analytical tests is one tool that can be utilized to meet this requirement. A Central Composite Design (CCD) was utilized for the validation of an LC‐MS/MS multi‐method for 84 analytes. The experimental design includes six design variables and two non‐design variables (response variables). Concentration, ionization temperature, dwell time, gradient, flow (of eluent), and spraying/curtain gas (continuous design variables) were varied on five different levels; the whole design encompassed 91 runs. To investigate the robustness of a LC‐MS/MS method both peak sensitivity and chromatographic separation had to be verified. Therefore, two non‐design variables were necessary. The distribution of the peaks over analysis time was applied to describe the quality of the chromatographic separation. The sensitivity was described with the signal to noise ratio (S/N). The evaluation of the measured data was accomplished with the Analysis of Variance (ANOVA) and the Response Surface Methodology (RSM). Three main effects (concentration, ionization temperature, dwell time) and no significant interaction effect were found for the response variable “S/N”. The variables of concentration, ionization temperature, and dwell time had no significant effects for the response variable “S/N”. The ANOVA of the response variable chromatographic separation abandoned no significant effects as well. Therefore, robustness of the method can be guaranteed for all non significant design variables.
Effect of obesity on prostate‐specific antigen recurrence after radiation therapy for localized prostate cancer as measured by the 2006 Radiation Therapy Oncology Group‐American Society for Therapeutic Radiation and Oncology (RTOG‐ASTRO) Phoenix consensus definition
Authors: Stroup Sean P. , Cullen Jennifer , Auge Brian K. , L'Esperance James O. , Kang Song K.
Published: July 2007

BACKGROUND.

Given the limited data regarding the impact of obesity on treatment outcomes after external beam radiation therapy (EBRT) for the definitive treatment of prostate cancer, the authors sought to evaluate the effect of obesity as measured by body mass index (BMI) on biochemical disease recurrence (BCR) using the most current 2006 Radiation Therapy Oncology Group‐American Society for Therapeutic Radiation and Oncology (RTOG‐ASTRO) Phoenix consensus definition (prostate‐specific antigen [PSA] nadir + 2 ng/mL).

METHODS.

A retrospective cohort study identified men who underwent primary EBRT for localized prostate cancer between 1989 and 2003 using the Center for Prostate Disease Research (CPDR) Multi‐center National Database. BMI was calculated (in kg/m2) and the data were analyzed. Univariate and multivariate Cox proportional hazards regression analyses were used to determine whether BMI significantly predicted BCR.

RESULTS.

Of the 1868 eligible patients, 399 (21%) were obese. The median age of the patients and pretreatment PSA level were 70.2 years and 8.2 ng/mL, respectively. Of 1320 patients for whom data were available with which to calculate PSA recurrence (PSA nadir + 2 ng/mL), a total of 554 men (42.0%) experienced BCR. On univariate analysis, BMI was found to be an independent predictor of PSA recurrence (P = .02), as was race, pretreatment PSA level, EBRT dose, clinical T classification, Gleason score, PSA nadir, and the use of androgen‐deprivation therapy (ADT). On multivariate analysis, BMI remained a significant predictor of BCR (P = .008).

CONCLUSIONS.

To the authors' knowledge, this is the first study to report the association between obesity and BCR after EBRT for localized prostate cancer as measured by the updated 2006 RTOG‐ASTRO definition. A higher BMI is associated with greater odds of BCR after undergoing definitive EBRT. Cancer 2007. Published 2007 by the American Cancer Society.
A peak load control‐based orchestration system for stable execution of hybrid services
Authors: Lee Yonghwan , Min Dugki
Published: July 2007

The prosperity of Internet results in a workflow executing engine's performance instability due to the request congestion for a short period of time. This paper proposes a peak load control (PLC) based orchestration system that can stably execute hybrid services. The PLC mechanism uses the delay time algorithm for controlling a BPEL engine's heavy peak load caused by the request congestion for a short period of time. In order to prove the stable performance of the PLC‐based orchestration system, we analyze the proposed delay time algorithm. According to our experimental results, the proposed delay time algorithm can stably execute structured activities of WSBPEL specification in heavily overloaded state after the saturation phase and has an effect on controlling the states of peak load. In this paper, we also describe a hybrid service architecture model that can represent both Web Services and existing EAs as same type of services. Copyright © 2007 John Wiley & Sons, Ltd.
Surfactant Fouling of Nanofiltration Membranes: Measurements and Mechanisms
Authors: Boussu Katleen , Kindts Céline , Vandecasteele Carlo , Van der Bruggen Bart
Published: July 2007

Fouling of nanofiltration membranes is studied during filtration of aqueous surfactant solutions under different conditions. To this purpose, four typical nanofiltration membranes (Desal51HL, NF270, NTR7450 and NFPES10) and three typical surfactants (nonionic neodol, anionic SDBS and cationic cetrimide) are selected. Fouling is studied as a function of the surfactant concentration, with and without addition of an electrolyte (NaCl), at different pH and when filtering a mixture of surfactants. Adsorption experiments and hydrophobicity measurements (to study the orientation of the surfactants on the membrane surface) are also performed under the different conditions. The least membrane fouling is found for the anionic surfactant SDBS, while for the cationic surfactant cetrimide very low relative fluxes are observed. Neodol shows an intermediate degree of fouling. Both hydrophobic and electrostatic interactions (in the case of ionic surfactants) between the membrane surface and the surfactant explain the degree of adsorption and hence fouling, as membrane fouling is correlated with the amount of adsorbed surfactant. The difference between cetrimide and SDBS becomes especially visible when changing the pH: increasing the pH leads not only to an opposite orientation of the adsorbed surfactants, but also to an opposite trend in adsorbed amount and membrane fouling. This study permits selection of an optimal nanofiltration membrane to recycle wastewater containing surfactants in the carwash industry. The optimal choice would be a hydrophilic membrane with a low molecular weight cut‐off and a small negative surface charge at neutral pH. Cationic surfactants in the wastewater should also be avoided as much as possible.
Die Dämpfung der Alfvénschen Wellen in der relativistischen Magnetohydrodynamik
Authors: Deutsch Rudolf V.
Published: July 2007

[Russian Text Ignored].
Zur statistischen Theorie der Diffusion geladener Teilchen
Authors: Ebeling Werner
Published: July 2007

A diffusion equation for a charged particle in an oscillating electric field is derived. We start with the Liouville equation for the distribution function of the whole system consisting of the host fluid and the charged particle. In order to obtain the time evolution of the distribution function of the charged particle in the coordinate space we utilize the technique of projection operators developed by Zwanzig. We find frequency‐ independent diffusion coefficients D = ζ(0) and frequency‐dependent mobilities B = ζ(ω)/kT. in terms of the correlation function magnified image Here ζ is the microscopic velocity of the charged particle and the average is over the equilibrium distribution function of the fluid in the presence of this charged particle. Under appropriate circumstances the correlation function ζ (omega;) may be computed by means of the Langevin‐Kirkwood equation. The relation between our theory and that obtained by Lebowitz and Resibois is discussed. We further show that at higher concentrations of charged particles the gradient of the concentration must be replaced by the gradient of the local osmotic pressure. The theory is applied to ambipolar diffusion.
Lösung der linearisierten Wlassow‐Gleichung für ein anisotropes Elektronenplasma
Authors: Bachmann P.
Published: July 2007

Es wird das Anfangswertproblem für die nichtrelativistische, linearisierte Wlassow‐Gleichung für ein Elektronenplasma in einem konstanten äußeren Magnetfeld untersucht. Diesem Anfangswertproblem ist eine Volterrasche Integralgleichung vom Faltungstyp für die Fourier‐Transformierte der Dichtestörung äquivalent. Mittels Laplace‐Transformation wird diese durch Berechnung des Resolventenkerns gelöst. Die Lösung, die nicht spezialisiert ist für bestimmte Verteilungsfunktionen, besteht wie für das magnetfeldfreie Plasma aus drei Anteilen: Der erste hängt nur von der Anfangsstörung ab; der zweite noch zusätzlich von der Gleichgewichtsverteilung; beide zeigen im allgemeinen kein zeitlich‐harmonisches Verhalten. Der dritte Teil hängt exponentiell von der Zeit ab, für ihn gilt eine “Dispersionsgleichung” (Landausche Lösung).

Für die folgende Anfangsstörung: f1(χ,v, t = 0) = g(v⊥, v|) exp (ik1·χ) wird die Dichtestörung genauer untersucht, wobei dann noch für g(v⊥, v|) eine Bi‐Maxwell‐Verteilung angenommen wird. Die beiden ersten Anteile, die nach Partialschwingungen mit den Frequenzen nωc entwickelt werden, zeigen im allgemeinen ein Transient‐Verhalten. Für den Fall der senkrechten Ausbreitung zum Magnetfeld wird gezeigt, daß alle Lösungsteile das gleiche zeitliche Verhalten zeigen; insbesondere wird auch für die Landausche Lösung im allgemeinen keine Dispersionsgleichung existieren.

Mit Hilfe des hergeleiteten Formalismus wird dann ein einfaches Anfangswertproblem für das kalte Plasma durchgerechnet.
Zur Theorie der künstlich erzeugten laufenden und stehenden Schichten. I
Authors: Fuchs Vladimir
Published: July 2007

Es wird gezeigt, daß im stabilen Regime nichttriviale, zeitlich asymptotische Lösungen des Systems der inhomogenen partiellen Differentialgleichungen der Ionisationswellentheorie existieren. Mit Rücksicht auf die Eindeutigkeit dieser Lösungen ergeben sich hiermit für eine günstig gewählte Quelle einzig mögliche Darstellungen der Wellenerscheinungen, die in einem zeitlich dauernd und räumlich lokal gestörten Plasma der positiven Säule ablaufen. Einige Grundeigenschaften dieser Lösungen stimmen gut mit Beobachtungen überein, die bei Experimenten mit künstlich erzeugten stehenden und laufenden Schichten gewonnen wurden, welche hinter einer lokalen stationären oder periodischen Störung entstehen.
Zur Ausbreitung von Wellen kleiner Amplitude in einem unvollständig ionisierten Plasma II
Authors: Wilhelm Johannes , Wisliceny Johann
Published: July 2007

Im ersten Teil unserer Arbeit [1] wurde unter dort im einzelnen angegebenen Bedingungen die Dispersionsgleichung (DpGl.) für ein Plasma hergeleitet, in welchem die Neutralteilchenkomponente wesentlich mit zu berücksichtigen ist (Abschnitt I). Die DpGl. wurde für fehlendes äußeres Magnetfeld (II) und für Wellenausbreitung parallel zu einem äußeren, homogenen und konstanten Magnetfeld (III) diskutiert. Nachstehend erfolgt die Diskussion der DpGl. für Ausbreitung der Wellen senkrecht zum äußeren Magnetfeld (IV)1). – Wir gebrauchen nachstehend die in [1] verwandten Bezeichnungen2). Zum Abschnitt IV wurden wie zu II und III einige Beispiele für Dispersionskurven berechnet und zwar für zwei der in I 4 beschriebenen Plasmen für jeweils zwei Werte der Feldstärke des äußeren Magnetfeldes. Zum Vergleich sind auch die Kurven für fehlendes Magnetfeld angegeben, die aus II und III übernommen wurden.
Experimentelle Ergebnisse zum stationären Anodenfall in der Niederdruck‐Edelgasentladung. Teil I
Authors: Zahn Rolf‐Jürgen , Schaal Günter
Published: July 2007

Nach einem Überblick zu den Anodenerscheinungen, den vorhandenen Modellvorstellungen und dem experimentellen Vorgehen im Anodengebiet der Niederdruckentladung wird über Ergebnisse von Anodenfallmessungen in Helium, Neon und Argon berichtet und ein qualitativer und quantitativer Vergleich mit der Theorie angeführt. Im Ergebnis wird auf deutliche Unterschiede zwischen Theorie und Experiment hingewiesen, deren Quellen in drei Problem‐komplexen bei der Beschreibung des Anodengebietes gesehen werden. Teil II der Arbeit unter‐nimmt es, durch gezielte Versuche Aussagen zu gewinnen, die zum vertieften Verständnis der anodischen Entladungserscheinungen beitragen können.
Modell der Plasmaexpansion
Authors: Hantzsche E.
Published: July 2007

Die Expansion eines kleinen Plasmavolumens infolge der Absorption eines kurzen Energieimpulses wird durch ein einfaches Modell beschrieben, mit den Annahmen: alle physikalischen Zustandsgrößen werden durch ihre räumlichen Mittelwerte ersetzt, und Ausgangsgleichungen sind hauptsächlich die Energie‐ und Impulsbilanz des gesamten Plasmas. Die Anfangsphase wird als stationär betrachtet. Damit lassen sich explizite Ausdrücke für die Expansions‐geschwindigkeiten, die kinetische und thermische Energie des Plasmas, die Temperaturen und Drücke gewinnen. Obwohl diese Beziehungen nur Näherungen sind, kann man qualitative und — in begrenztem Maße — auch quantitative Aussagen ableiten. Beispielsweise liegt die kinetische Expansionsenergie zwischen 1/5 und 1/2 der absorbierten Gesamtenergie W0, und die mittlere Temperatur T wächst während der Expansion ∼ W02/5.
Die Geschwindigkeitsverteilung der Ionen in der Freifallsäule
Authors: Valentini H.‐B.
Published: July 2007

The velocity distribution of the ions in the positive column of the free‐fall type discharge is derived by means of the method of characteristics from collisionless Boltzmann equation extended by a source term in plane and cylindrical geometries. A homogeneous axial magnetic field and the initial distribution of ion velocities is taken into account. The formula of Tonks and Langmuir for ion density is reproduced in case of vanishing initial velocity of the ions and vanishing magnetic field.
Stability of Waves in Relativistic Plasma
Authors: Gupta R. M. , Varma N. L.
Published: July 2007

The dispersion relation of electromagnetic waves propagating perpendicular to an applied uniform magnetic field B0 in relativistic plasma is derived. Waves propagating perpendicular to the uniform applied magnetic field can be separated into two modes ‐ one is the linearly polarized transverse wave and the other is a hybrid mode. In the present analysis, dispersion relation of the first mode i. e., for a pure transverse wave is analysed under the assumption that the wavelength is much longer than the cyclotron radii of the electrons. A stability criterion which limits the thermal energy of the electrons along B0 is obtained.
Über stationäre, rotierende, inkompressible Plasmen mit minimalen inneren Verlusten
Authors: Schäfer D.
Published: July 2007

Die Forderung, daß nicht nur die Ohmschen, sondern auch die Verluste durch innere Reibung minimalisiert werden sollen, führt zu dem Ansatz, daß sowohl das Magnetfeld H als auch das Geschwindigkeitsfeld v Trkal‐Felder sind:

equation image

mit konstantem α, β. Im rotationssymmetrischen, stationären Fall folgt aus der Bedingung, daß die zum Rand senkrechte Komponente von v, v ⊥ und die toroidale Komponente vφ bzw. H⊥ und Hφ auf dem Rand verschwinden, ein lineares Eigenwertproblem für α, β, das sich insbesondere für rechteckige Grundbereiche leicht lösen läßt.

Es ergibt sich:

equation image
.
Zur Theorie der parametrischen Anregung von elektrostatischen Oberflächenwellen in einer Plasmaschicht
Authors: Aliew Ju. M. , Gradow O. M. , Sünder D.
Published: July 2007

Dispersion relations for electrostatic surface waves in a homogeneous plasma‐layer which interacts with an external electric pumping field parallel to the boundaries are derived in the framework of the kinetic theory. The parametrically excited and purely growing instabilities are investigated. Electric threshold fields and growth rates for the instable surface modes are given. It can be shown that the minimum threshold for parametric excitation occurs for those modes which are symmetric about the midplane of the layer.
Anomales Verhalten des Säulenplasmas von Edelgasentladungen im longitudinalen Magnetfeld
Authors: Deutsch H. , Pfau S.
Published: July 2007

Es wurden systematische Messungen der axialen elektrischen Feldstärke im Plasma der positiven Säule stromschwacher Entladungen in den Edelgasen Helium, Neon, Argon und Krypton in Abhängigkeit vom longitudinalen Magnetfeld durchgeführt. Überraschenderweise zeigen die erhaltenen Ergebnisse, daß der Säulengradient mit wachsendem Magnetfeld zunächst ansteigt, um erst nach dem Durchlaufen eines flachen Maximums abzusinken. Dieses im Gegensatz zu den Aussagen der klassischen Diffusionstheorie des Säulenplasmas im Magnetfeld stehende Verhalten konnte in allen Edelgasen beobachtet werden. Die charakteristischen Werte der magnetischen Induktion Bm/p0 für das Maximum hängen nur schwach von den Entladungsparametern ab und betragen für Helium 300 G/Torr, für Neon 500 G/Torr, für Argon 1000 G/Torr und für Krypton etwa 1500 G/Torr. Als Ursache für das Auftreten des Maximums im Gradienten wird die radiale Änderung der Energie‐verteilung der Elektronen in Abhängigkeit vom longitudinalen Magnetfeld angesehen.
A New Model of Crater Formation by Arc Spots
Authors: Hantzsche E.
Published: July 2007

The forces acting on the cathode arc spot surface and removing the molten layer from the crater bottom are composed mainly of the ion pressure, the neutral gas pressure and the evaporation recoil whilst electrostatic forces diminish the effective pressure that is in the order of some 109 dyn/cm2. The motion of the liquid layer caused by these forces is treated with the hydrodynamic equations. A simple solution exists in the special case of constant layer depth, that is achieved a few nanoseconds after spot formation. From this model the layer depths (some 0.1 μm) and the ejection velocities at the crater rims (few 104 cm/s) are calculated. The real spot velocity agrees with the velocity of the melting front below the spot surface, but because of the stochastic character of the spot motion the apparent velocity decreases with growing observation time intervals Δt according to Δt−1/2.
Non Equilibrium Vibrational Population and Dissociation Rates of Oxygen in Electrical Discharges: The Role of Atoms and of the Recombination Process
Authors: Cacciatore M. , Capitelli M. , Dilonardo M.
Published: July 2007

The influence of oxygen atoms on the population densities of vibrational levels of molecular oxygen has been studied for discharge conditions in which the atoms come 1) from electronic transitions to Herzberg and Schumann systems 2) from the pure vibrational mechanism (PVM) discussed in Chem. Phys. 30 (1978) 95.

In the first case the atoms deactivate the first vibrational levels of O2, thus reducing the vibrational temperature and the propagation of the introduced vibrational quanta by V — V exchanges.

Under these conditions PVM disappears. An assisted recombination dissociation mechanism, however, holds in these conditions, due to the recombination process which induces a strong disequilibrium on the levels near to the dissociation continuum. These levels can redissociate by collisions with heavy particles.

The results of pure vibrational mechanism in the presence of atoms are very similar to those discussed in our previous work. The production of oxygen atoms self adjusts to small values due to the increased importance of V — T deactivation by oxygen atoms.
[Russian Text Ignored]
Authors: [Russian Text Ignored]
Published: July 2007

This paper is devoted to the investigation of a turbulent heated beam discharge plasma in the molecular gas hydrogen as an example. We are interested in the stationary behaviour of this plasma type under the condition of weak Langmuir turbulence and under the action of several kinds of interaction processes. This discharge plasma is of increasing importance especially from the point of plasmachemical purposes.

At first we give a short development of the kinetic equation employed including the Coulombinteraction between the charged particles as well as the different kinds of binary collision processes between electrons and non‐exited molecules. The essential parameters in this description are the full energy density of the Langmuir turbulence per one electron e0Ū = W/ne and the degree of ionization ne/N. In a broad range of these two parameters Ū and ne/N, which are typical for a beam discharge plasma, we determined numerically the velocity distribution function of the electrons and with the aid of this especially the mean energy, the energy gain from the turbulent field, the frequencies for the several collision processes as well as the energy losses due to the binary collisions and the Coulomb interaction between electrons and ions.

In particular we investigated the main energy channels by which the energy of the electrons is transfered into the several degrees of freedom of the molecular gas and into the ion component.
Selfconsistent Electron Energy Distribution Functions in Non Equilibrium oxygen: Effects on the Dissociation Rate
Authors: Capitelli M. , Dilonardo M. , Gorse C.
Published: July 2007

Electron energy distribution functions (edf) in non equilibrium oxygen have been calculated by solving the Boltzmann equation coupled to a system of vibrational master equations. The results show the importance of both superelastic vibrational collisions and of the presence of oxygen atoms in affecting edf.

The coupling between the Boltzmann equation and the system of vibrational master equations brings to a temporal evolution of edf, which progressively changes from a cold molecular gas situation (all molecules in the ground vibrational level) to a vibrationally excited molecular gas and finally to a gas composed by oxygen molecules and oxygen atoms.

All electronic rate coefficients follow a temporal evolution. due to the corresponding evolution of edf.

Finally the present results are used for discussing the dissociation rate of molecular oxygen in electrical discharges.
Nonlinear Resonant Interaction of Three Extra‐ordinary Waves in a Hot Electron Plasma
Authors: Das K. P. , Sihi S.
Published: July 2007

The coupled mode equations and coupling coefficients for the resonant nonlinear interaction of three extra‐ordinary waves in a hot magnetized plasma are derived by Whitham's method of averaged Lagrangian. The wave vectors of the three waves are taken as noncollinear and perpendicular to the external uniform magnetic field. Of the three waves one is of high frequency mode and the other two are of low frequency mode.
Relaxation of Plasma Electrons towards Stationary States as Related to Different Initial Energy Distributions and for a Wide Range of the Final Electric Field Strength
Authors: Wilhelm J. , Winkler R.
Published: July 2007

Starting from former investigations concerning the collision dominated relaxation of the electron component in weakly ionized inert gas plasma we generalize the results obtained. Also in the present paper we use the same adaquate kinetic equation for the electron energy distribution function. On one side the influence of non‐stationary, analytically given initial energy distributions on the relaxation behaviour and on the resulting adjustment time of stationary states was investigated. On the other side the calculation, especially of the adjustment time, was extended to a whole variety of final stationary states ranging from those determined only by energy loss due to elastic collisions to those determined only by exciting collisions. The adjustment time obtained varies by about four orders of magnitude within this wide range of final stationary states.
Diffusionstheoretische Beschreibung der Dissoziation und des Ionenhaushaltes im schwachionisierten Säulenplasma der Wasserstoffentladung. III. Kenngrößen der positiven Säule bei verschiedenen Drücken (0,3 … 10 Torr) und Strömen (10−4 … 1 A)
Authors: Michel P. , Pfau S. , Rutscher A. , Winkler R.
Published: July 2007

Auf der Grundlage der Lösung der Boltzmann‐Gleichung für das Elektronengas werden die Teilchenbilanzen verschiedener Ionen (H+, H2+, H3+, H3+, H5+) und der neutralen Komponenten im H/H2‐Säulenplasma unter Berücksichtigung zahlreicher Elementprozesse (Volumen‐ und Wand‐prozesse) diskutiert. Dies liefert ein detailliertes Verständnis der elektrischen Charakteristik des Plasmas in Verbindung mit der chemischen Zusammensetzung des Gases. Im Bereich kleiner Drücke und höherer Ströme treten große Dissoziationsgrade auf. Experimentelle Untersuchungen bestätigen diese theoretischen Ergebnisse. Auf noch bestehende Unterschiede zwischen der gemessenen und berechneten elektrischen Charakteristik wird hingewiesen.
Diffusionstheoretische Beschreibung der Dissoziation und des Ionenhaushaltes im schwachionisierten Säulenplasma der Wasserstoffentladung. IV. Grenzfälle der experimentell realisierbaren Druckbilanz — Variation der Gastemperatur — Ähnlichkeitsdarstellung der Plasmaparameter
Authors: Michel P. , Pfau S. , Rutscher A. , Winkler R.
Published: July 2007

In den vorausgegangenen Teilen dieser Arbeit wurde ein Bilanzgleichungssystem zur mikro‐physikalischen Beschreibung des Wasserstoffplasmas hergeleitet, die Elektronenkinetik im H/H2‐Mischplasma analysiert und Ergebnisse über die Berechnung der inneren Säulenparameter für verschiedene Entladungsbedingungen vorgestellt. In Fortsetzung dieser Arbeiten werden in diesem Teil der Einfluß zweier Grenzfälle der Druckbilanz und der Änderung der Neutralgastemperatur auf die inneren Säulenparameter untersucht sowie die Frage der Ähnlichkeitsdarstellung der makroskopischen Säuleneigenschaften behandelt.
Influence of Electrode Material on Time Delay of Electrical Breakdown in Gases
Authors: Pejović M. M. , Bošan Dj. A. , Krmpotić Dj. M.
Published: July 2007

A significant correlation between the work function of electrode material and the statistical time delay of electrical breakdown in nitrogen‐filled diodes has been established. The results obtained confirm that time delay of electrical breakdown increases with increasing of electrode material work function.
On the Averaged Forces in Bounded Plasma in Parallel Electric and Magnetic Fields
Authors: Nikolov N. A. , Malinov P. N. , Yanovsky A. B.
Published: July 2007

Averaged forces of Miller's type, acting on the particles of a bounded plasma in parallel external a. c. electric and d. c. magnetic fields, are found on the basis of the equations of the two‐component MHD. It is assumed, that standing transverse waves are excited in the plasma by the external source before the a. c. electric field is switched on.
Interaction of a Low Frequency Coherent Magneto‐Acoustic Wave with a Turbulent Spectrum of Extra‐Ordinary Waves
Authors: Das K. P. , Sluijter F. W.
Published: July 2007

Starting from nonlinear evolution equations of a three‐dimensional extra‐ordinary wavepacket in a magnetized plasma and introducing a correlation function, equations are derived that describe interaction of a coherent low‐frequency magneto‐acoustic wave with a turbulent spectrum of high frequency extra‐ordinary waves. These equations are used to derive the dispersion relation for a low frequency magnetoacoustic wave in the presence of a spectrum of turbulent high frequency extra‐ordinary waves. In the narrow spectrum case, it is found that a small but finite spread in the spectrum of turbulence has a stabilizing influence on the instability which exists for vanishing spectral width. In the wide spectrum case, the effect of a weak turbulent spectrum of extra‐ordinary waves is to produce a slight shift in frequency of the coherent low frequency magneto‐acoustic wave and to damp or excite the wave.
Kinetic Study of Electron Beam Excited Argon
Authors: Bretagne J. , Godart J. , Puech V.
Published: July 2007

An experimental and theoretical study of the interaction between Argon and a high‐energy short‐pulse electron beam is reported. A theoretical model describing the argon atom and molecule with ten effective levels and taking into account all the reactions that these levels may suffered is developped. A comparison, based on time resolved V.U.V. and visible fluorescences and electron density determination, between the theoretical and experimental results shows the ability of our model to describe the interaction in all the experimental range, 400 < P < 5000 Torr, studied.