bluuebunny/crossref_metadata_2025 huggingface dataset:
Stellar populations and dust in the galaxy NGC 2976, a low‐luminosity member of the M81 group
Authors: Bronkalla W. , Notni P. , Mutter A. A.‐R.
Published: July 2007

Photographic UBV photometry of NGC 2976, a low‐luminosity member of the central M81 group of galaxies, is presented. Young stars in the central disk determine the optical view and the classification of this Sc(pec) galaxy. It is surrounded by a halo of an old population which contains nearly all the mass and half the luminosity of the system. This halo has some properties typical of spheroidal dwarf galaxies: an exponential brightness profile, an ellipticity trend of the isophotes typical of low‐mass systems, and mass and luminosity near the upper limit of typical dwarfs. In the central population I disk, star formation proceeds in dense associations scattered irregularly in a broad ringlike region of 1.2 kpc radius just inside the turnover of the rotation curve. This star formation episode may last since some 108 a; it is possibly triggered by gas infall from the interstellar cloud generated during encounters between other group members in the central M81 group. A direct triggering by recent encounters is excluded since NGC 2976 is undisturbed in its outer parts.
On the photographic detection of novae: a specific case in Libra
Authors: Debehogne H.
Published: July 2007

Comparing ESO GPO astrograph plates taken in September 1990 at La Silla with the Palomar Sky Survey from 1955, a nova was ostensibly discovered at α = 15h07m31s, δ = −1°44′01″.6 (equinox 1950.0). Its magnitudes in 1955 estimated from the Palomar plates are mB = 16·m9 and mR = 17·m. Finally (March 1991), it was identified as a high redshift (z ∼ 0.3) galaxy (Rafanelli, private communication) by spectroscopic means. Radio observations are requested.
Looking for a massive KeV pseudo‐scalar in gamma ray bursts
Authors: Wolf C.
Published: July 2007

Looking for repetitive signals within a γ burst may provide evidence for a massive KeV pseudo‐scalar coupled to electromagnetism. We study the possible signatures that may occur for pseudo‐scalar electromagnetic propagation and outline possible probes to the pseudo‐scalar mass as well as its coupling to electromagnetism.
Elliptic integrals for cosmological constant cosmologies
Authors: Feige B.
Published: July 2007

Following the discussion of some general properties and analytical formulae for cosmological models with non‐zero cosmological constant, we show how the elliptic integrals for comoving distance and light travel times as function of redshift can be expressed through Legendre integrals of the first and third kind, for which standard implementations are readily available. Observational properties are then illustrated for selected but typical models using the previously derived formulae.
Rapid oscillations of five stars in the spectral range A and F. I
Authors: Hildebrandt G.
Published: July 2007

The five stars HD 4849, HD 24712, HD 182475, HD 184552 and HD 215874 are a small group of objects enclosed in a larger observational programme for searching of rapid oscillations. They have been observed with the 50 cm ESO‐telescope at La Silla (Chile). These objects are characterized as a suspected δ Scuti‐type star, an Ap star, an A9 V star, an A1m star and an A9 III‐IV star, respectively. For the first two stars the periods, dedected by other authors, were confirmed. For HD 182475 a period of 112.3 min has been estimated. In the case of HD 184552 an oscillation with a period of 163.3 min has been found. The star HD 215874 shows unambiguously a variation with a period of 97.2 min.
Lymanα forests and the evolution of the universe
Authors: Liebscher D.‐E , Priester W. , Hoell J.
Published: July 2007

The Lyα forest absorption lines in the spectra of quasars are interpreted as caused by the crossings of the light beam with the walls of a bubble structure (expanding with the Hubble flow only). Then, the typical separation between the absorption lines is proportional to the mean size of the bubbles. The variable factor is the expansion rate H[z]. The Friedmann regression analysis of the observed line separations determines the density parameter ω0 and the normalized cosmological term λ0 = λc2/3H20 of the appropriate cosmological model:

ω0 = 0.014 ± 0.002,

λ0 = 1.080 ± 0.006.

Depending on the Hubble parameter this method reveals the values of the present mean matter density pm,0 = 2.6 h2 · 10−28 kg m−3 and of the cosmological constant Λ = 3.77 h2 · 10−52 m−2 (with h = H0/(100 km/s·Mpc)). According to our analysis all models with Λ = 0 must be excluded. The curvature of space is positive. The curvature radius R0 is 3.3 times the Hubble radius (c/H0). The age t0 is 2.8 times the Hubble age (H0−1).
Cosmological evolution driven by viscous dissipation and monopole condensation in ten dimensions
Authors: Wolf C.
Published: July 2007

A ten dimensional cosmology is studied wherein the stringy state of the early universe is simulated by a combination of viscous effects and monopole condensation in the primeval ten dimensions.
The 100—year periodic modulation of solar rotation
Authors: Yoshimura H. , Kambry M. A.
Published: July 2007

A periodic long‐term modulation of the solar surface rotation with a time scale on the order of 100 years is found in the sunspot data from 1874 to 1992 obtained by combinig the Greenwich Photoheliographic Results from cycle 11 to cycle 20 analysed by Balthasar, Vázquez, and Wöhl and the Mitaka sunspot sketch data from cycle 18 to 22 of the National Astronomical Observatory of Japan which was the Tokyo Astronomical Observatory of the University of Tokyo until 1988. A new index of the solar rotationMdefined by integrating the angular momentum density over the whole surface, which we call the angular momentum surface layer density, reached a maximum at solar cycle 14, decreased to a minimum at cycle 17, and then increased to reach another maximum at cycle 21. The increase ofMmeans acceleration of the surface layer as a whole by transport of angular momentum from the deeper layer. This implies an decrease (increase) of the radial gradient of the differential rotation if the basic radial gradient of the differential rotation increases (decreaes) inward. The decrease ofMmeans deceleration of the surface layer and implies an increase (decrease) of the radial gradient. The degree of the equatorial acceleration of the surface differential rotation is also found to have undergone the same 100 year periodic modulation during the same interval, reaching a minimum at cycle 14, a maximum at cycle 17, and a minimum at cycle 21 in antiphase with the modulation ofM. Thus both radial and latitudinal gradients of the differential rotation increased and decreased in phase (in anti‐phase) if the basic radial gradient increases (decreases) inward.
Determination of proper motions for AC stars: First results
Authors: Volchkov A. A. , Kuzmin A. V. , Nesterov V. V. , Bastian U. , Röser S.
Published: July 2007

Proper motions of the stars of the Astrographic Catalogue are being derived, using the Hubble Space Telecope Guide Star Catalogue as second epoch. Results on the San Fernando and Cordoba AC zones are presented. Identification with GSC stars (i.e. determination of proper motion) was successful for 97 percent of all AC stars. Comparison of the proper motions thus derived with those of Preliminary PPM South shows that the accuracy is about 0.8 to 0.9 arcsec per century. Thus we can derive proper motions for about 4 million stars, with an accuracy higher than that of the SAO Catalogue.
Der Informationsgehalt langbelichteter Sternaufnahmen
Authors: Müller R. , Geyer E. H.
Published: July 2007

With this paper we present the mathematical background for a novel method for the deconvolution of longer exposed double star images, merged by seeing and other effects. This method, which was recently presentcd in a short paper (Müller and Geyer 1993) makes use of the autocorrelation of the odd function of the merged, and thus asymmetric two dimensional double star image profile. We give the mathematical evidence that digital filtering during the image processing does not influence the angular distance of the binary components, and that it can be determined independently of the brightness difference of the components. The brightness difference itself can be obtained without ambiguity, if it does not exceed 3 mag, and then the distance has been derived before. We further show that the information content of stellar images is generally less degraded by seeing effects as was previously supposed. Thus closer double stars can be resolved and photometrically deconvoluted by the method. By atmospheric disturbances, telescope guiding errors, optical distortions and silhouetting generally the stellar images on astrometric photographs of modern opto—electronic detectors are asymmetrically deformed. Therefore, the method yields also better accuracy and more adequate results for astrometry, photometry, and also astropspectroscopy.
Zum optischen Langzeitverhalten von AM Herculis I. Das Beobachtungsmaterial, die Langzeitlichtkurve und der bahninduzierte Lichtwechsel
Authors: Götz W.
Published: July 2007

Für den veränderlichen Doppelstern AM Herculis, der den Prototyp einer Untergruppe von kataklysmischen Sternen darstellt, werden Untersuchungsergebnisse über das Langzeitverhalten mitgeteilt. Der nachfolgende Teil der Publikation bezieht sich auf das Beobachtungsmaterial, die Langzeitlichtkurve und die bahninduzierten Helligkeitsänderungen. Auf der Grundlage von 1275 photographischen Beobachtungen in B, V and U, die meisten von ihnen in B, die das Zeitintervall zwischen den Jahren 1982 und 1991 überdecken, können neue Aussagen über das allgemeine photometrische Verhalten des Sternes, dessen inaktive und angeregte Zustände sowie die gegenseitigen Beziehungen unter ihnen, die einzelnen Einflüsse der bahninduzierten Helligkeitsänderungen auf die Gesamthelligkeit und nicht zuletzt über das Farbverhalten des Sternes innerhalb der einzelnen Erscheinungen und des gesamten Zeitintervalls, das Gegenstand des zweiten Teils dieser Untersuchung ist, gemacht werden.
Zum optischen Langzeitverhalten von AM Herculis. II. Das Farbverhalten
Authors: Götz W.
Published: July 2007

In Ergänzung und Vervollständigung der Ergebnisse aus dem ersten Teil dieser Publikation (Götz, 1993) wurde das Langzeit‐Farbverhalten von AM Her auf der Grundlage von 138 (B — V)– und 136 (U — B)‐Farbenindizes untersucht. Die photometrischen Parameter des engen Doppelsterns und die Spektraltypen seiner Komponenten konnten abgeleitet werden. Es konnte auch gezeigt werden, daß die meisten Einflüsse, die den unterschiedlichen Farben‐Helligkeits‐Diagrammen überlagert sind, durch eine zusätzliche Lichtquelle hervorgerufen werden, die im inaktiven Zustand den stellaren Materiestrom und im aktiven Stadium das polare Emissionsgebiet charakterisiert. Das entwicklungsbedingte Verhalten dieser Erscheinungen wird in allen Farben‐Helligkeits‐Diagrammen durch typische Merkmale angezeigt.
Micrometer measurements of visual double stars at Calar Alto
Authors: Ling J. F. , Lanchares V.
Published: July 2007

We present 93 micrometer measurements of 55 double stars observed with the 152 cm telescope at the Spanish observatory at Calar Alto (Almeria, Spain).
Photometric catalogue of Shakhbazian compact groups of galaxies. II
Authors: Stoll D. , Tiersch H. , Oleak H. , Baier F. , Macgillivray H. T.
Published: July 2007

The second part of the photometric catalogue of Shakhbazian compact groups of galaxies contains optical and geometrical properties of another 24 groups (Shkh 264, 265, 266, 267, 268, 269, 270, 271, 272, 273, 274, 275, 276, 277, 278, 279, 280, 281, 282, 283, 284, 285, 286, 287). As in the first paper photometric data were obtained from the COSMOS/UKST catalogue of the Southern sky with δ ≤ +2°30′. The survey of compact galaxy groups by Shakhbazian, Petrosian, Baier, and Tiersch is a basis for studying dynamical processes in such groups.
Optical and X‐ray structures of galaxy clusters. I
Authors: Baier F. W. , Lima G. B. , Wipper H. , Braun M.
Published: July 2007

The differences between optical and X‐ray structures of galaxy clusters are discussed. We analyse in detail 7 Abell clusters. There is an increasing number of arguments in favour of different distributions of galaxies, gas, and dark matter in many clusters. We argue that most clusters present sub‐structures at least in the gaseous and galactic components and, moreover, the subclustering of different components does not always coincide. Such arguments strongly support the idea that most galaxy clusters are by far more complex systems than accepted until now and are usually not in an hydrostatic isothermal equilibrium.
On the question of radio emission of spiral galaxies in groups of galaxies
Authors: Malumian V. H.
Published: July 2007

It has been shown that the radio emission properties of spiral galaxies, if the other conditions are the same, are determined rather by the presence of the close neighbours than by space density of galaxies around them. The rate of occurence of radio sources and their radio luminosities among the spiral members of groups of galaxies depend on the projected seperation between them and their nearest neighbour. The shorter this seperation the higher the probability of radio emission.
Astrometric positions of comet Hale‐opp (1995 O1) in 1995
Authors: Ikbal M. A. , Irfan M. , Raharto M. , Hidayat B.
Published: July 2007

Nine positions of comet Hale‐Bopp (1995 O1), derived from the X‐Y positions on Bosscha Schmidt plates, taken between August 15 to August 22, 1995, are given.
Photometric variability of the Herbig Ae/Be star HD 200775
Authors: Sūžius J. , Sperauskas J.
Published: July 2007

We present results of photometric monitoring of HD 200775 in the passbands X and V of the VILGEN system obtained over the period from September 1994 to May 1995. It is shown that the star varies with a period of 10.225±0.041 days and an amplitude of 0.02 mag in X passband. The variations on the time scale of several hours and/or days are also confirmed.
Interactions of high velocity clouds with the disk of the LMC
Authors: Braun M.
Published: July 2007

High‐resolution (∼1′0…2′4) IRAS maps, optical broad‐band, and narrow‐band images as well as H 1 λ 21 cm data have been used in order to analyse the environment of two large‐scale distortions (LMC 4 and DEM 268) in the disk of the Large Magellanic Cloud. This study has revealed cone‐like structures connected to DEM 268 and LMC 4 indicating high‐velocity cloud impacts as the most probable source of the formation of these two distortions. In both cases, the tip of the cone, which is a place of increased star formation, has a shape which is typical of supersonic motion of gaseous matter through a compressible medium. Expansion velocities of the cone‐like structures of about 12 km·s−1 can be derived from the H 1 λ 21 cm data. From these velocities, ages of the distortions of about 40 Myr (LMC 4) and 36 Myr (DEM 268) are estimated. The energy input for the formation of the distortions might have been provided by high velocity clouds with masses of the order of 105 M⊙ (assuming an initial velocity of 100 km·s−1 relative to the disk of the LMC).
Catalogue of Shakhbazian compact groups of galaxies. VII.
Authors: Stoll D. , Tiersch H. , Braun M.
Published: July 2007

The seventh part of the catalogue of Shakhbazian groups contains the positions and references of all the galaxies of the following 48 groups (north of δ > +2°30′): Shkh 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 142, 149, 150, 153, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166. For the estimation of the coordinates the Digitized Sky Survey was used.
New and misclassified Planetary Nebulae
Authors: Kohoutek L.
Published: July 2007

Altogether 86 objects discovered in the period 1991–1994 have been accepted by the author as new PN (Table 1). In Appendices A and B to this table the lists of possible pre‐PN as well as of possible post‐PN, respectively, are given. Table 2 presents 6 misclassified objects which we suggest removing from CGPN.
Large‐scale transport of plasma in the Earth's plasma sheet: comparative analysis for adiabatic and non‐adiabatic cases
Authors: Zakharov V. E. , Meister C.‐V.
Published: July 2007

A system of multi‐fluid MHD‐equations is used to compare adiabatic and non‐adiabatic transport of the energetic particles in the magnetospheric plasma sheet. A “slow‐flow” approximation is considered to study large‐scale transport of the anisotropic plasma consisting of energetic electrons and protons. Non‐adiabatic transport of the energetic plasma is caused by scattering of the particles in the presence of both wave turbulence and arbitrary time‐varying electric fields penetrating from the solar wind into the magnetosphere. The plasma components are devided into particle populations defined by their given initial effective values of the magnetic moment per particle. The spatial scales are also given to estimate the non‐uniformity of the geomagnetic field along the chosen mean path of a particle. The latters are used to integrate approximately the system of MHD‐equations along each of these paths. The behaviour of the magnetic moment mentioned above and of the parameter which characterizes the pitch‐angle distribution of the particles are studied self‐consistently in dependence on the intensity of non‐adiabatic scattering of the particles. It is shown that, in the inner magnetosphere, this scattering influences the particles in the same manner as pitch‐angle diffusion does. It reduces the pitch‐angle anisotropy in the plasa. The state of the plasma may be unstable in the current sheet of the magnetotail. If the initial state of the plasma does not correspond to the equilibrium one, then, in this case, scattering influences the particles so as to remove the plasma further from the equilibrium state. The coefficient of the particle diffusion across the geomagnetic field lines is evaluated. This is done by employing the Langevin approach to take the stochastic electric forces acting on the energetic particles in the turbulent plasma into account. The behaviour of the energy density of electrostatic fluctuations in the magnetosphere is estimated.
VRI photometry of the Einstein Cross Q2237+0305 at Maidanak observatory
Authors: Vakulik V. G. , Dudinov V. N. , Zheleznyak A. P. , Tsvetkova V. S. , Notni P. , Shalyapin V. N. , Artamonov B. P.
Published: July 2007

Observations of the gravitationally lensed quasar Q2237+0305 were made with the 1.5‐meter AZT‐22 telescope at Maidanak (Uzbekistan) on 17–19 September 1995. All four components of the quasar are clearly resolved. The results of photometric measurements of the components are presented. It is confirmed that the component A again became the brightest one in the system. A noticeable change of the mutual colours of the components A and B in comparison with previous observations is detected and discussed. We cannot decide, on the basis of existing observational data, whether varying extinction or “chromatic” microlensing is the cause. Stronger, correlated colour changes in the system are probably caused by quasar variability. The dominant time scale of the microlensing‐governed brightness variations since the discovery is of the order of 10 years. A correlation between radio brightness and optical colour is found but cannot be explained.
Catalogue of Shakhbazian compact groups of galaxies. IX
Authors: Stoll D. , Tiersch H. , Cordis L.
Published: July 2007

The nineth part of the catalogue of Shakhbazian groups contains the positions and references of all the galaxies of the following 48 groups (north of δ < +2°30'): Shkh 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 253, 254, 255, 256, 257, 258, 259, 260, 328, 338, 339, 340, 340a. For the estimation of the coordinates the Digitized Sky Survey was used.
Search for magnetic field oscillations in a sunspot umbra
Authors: Landgraf V.
Published: July 2007

In order to search for oscillations in velocity and magnetic field strength within a sunspot umbra, a time series of spectra has been obtained through a circular analyzer and the Gregory‐Coudé telescope at the Observatorio del Teide, Tenerife. The velocity oscillations clearly show peaks of power at periods between 2 and 7 minutes, with a maximum at 5 minutes. The apparent variations of the magnetic field strength, however, don't exhibit significant oscillations; these fluctuations are rather produced by the influence of parasitic stray light from the surrouding quiet sun which are also visible in the measured time variations of the umbral contrast of continuum intensity.
ROSAT public PSPC observations in the Las Campanas Redshift Survey
Authors: Tucker D. L. , Hasinger G. , Lin H.
Published: July 2007

The Las Campanas Redshift Survey, an optically selected survey which contains 26 418 galaxy redshifts, has been correlated with “The First ROSAT Source Catalogue of Pointed Observations with the PSPC,” which contains 50 408 sources from 2876 ROSAT pointed observations. Ten matches were found. The optical spectra of most of the ten matches show weak narrow emission lines. Due to their high x‐ray luminosities, their high x‐ray‐to‐optical flux ratios, and the evidence of rapid x‐ray variability in the two brightest matches, we interpret the majority of these objects to be narrow‐line Seyfert galaxies or “hidden” active galactic nuclei. Of the ten matches, only one galaxy shows the characteristics of a bona fide starburst.
The axial angular momentum of the general circulation of the oceans
Authors: Brosche P. , Wünsch J. , Maier‐Reimer E. , Segschneider J. , Sündermann J.
Published: July 2007

With the Hamburg geostrophic ocean general circulation model, the temporal variation of the angular momentum of the oceans is studied. The input wind stresses consist of climatological winds plus the deviations of the actual winds 1981–1989. The motion part of the angular momenta of the two hemispheres resembles the (counter‐phase) behaviour of the corresponding atmospheric angular momentum. The dominating matter part however shows no phase shift between the hemispheres. The sum of the angular momenta of the solid Earth and the atmosphere is deduced from observations; in principle it should be inversely correlated to the oceanic angular momentum. A first attempt to recognize the correlation between these empirical data and the theoretical values is described.
Narrow‐line Seyfert 1 galaxies
Authors: Boller Th.
Published: July 2007

This paper summarizes the soft X‐ray properties of narrow‐line Seyfert 1 galaxies (NLS1). NLS1 have generally steeper soft X‐ray continuum slopes than Seyfert 1s with broader lines, and there exists an anticorrelation between 0.1–2.4 keV continuum slope and the FWHM of the Hβ line. Objects with steep 0.1–2.4 keV continuum slopes and Hβ FWHM > 3000 km s−1 are clearly discriminated against by nature. When simple power‐law models are fit to the data, photon indices reach values up to about 5, much higher than is usually seen in Seyfert 1s. Models with smaller mass black holes and/or higher Eddington fractions show some promise to explain the relation between the FWHM of the Hβ line and the X‐ray continuum slope. We further report evidence for persistent gaint and rapid variability in the ultrasoft narrow‐line Seyfert 1 galaxy IRAS 13224–3809. We have examined possible explanations for the gaint variability. Unusually strong relativistic effects provide a plausible explanation of the X‐ray data. Relativistic boosting effects may be relevant to understanding the strong X‐ray variability of some steep spectrum Seyferts more generally.
First Beppo‐SAX results on AGN
Authors: Guainazzi M. , Piro L.
Published: July 2007

In the following paper, some first Beppo‐SAX results on AGN are presented. Main on‐flight calibration features and observational properties are discussed at the light of possible future AGN studies.
TRAFICOS – an Échelle Zeeman spectrograph
Authors: Hildebrandt G. , Scholz G. , Rendtel J. , Woche M. , Lehmann H.
Published: July 2007

We describe the TRAnsportable Flbre COupled échelle Spectrograph (TRAFICOS) equipped with a Zeeman analyzer and manufactured mainly for the observation of stellar magnetic fields. The spectrograph, designed at the Astrophysikalisches Institut Potsdam and constructed at the Thüringer Landessternwarte Tautenburg, is laid out in a quasi‐Littrow configuration. The part attached to the Nasmyth focus of the 2 m telescope contains the telescope adapter for the fibre input and output of the star and calibration light, the cases for the flatfield and the wavelength calibration, and the Zeeman analyzer. The optical scheme and the reduction software are mentioned in some details and the first results of the determination of the magnetic field and radial velocity of several stars are given showing the performance of the device in comparison with existing data.
Inhomogeneous potentials producing homogeneous orbits
Authors: Bozis G. , Anisiu M.‐C. , Blaga C.
Published: July 2007

We prove that, in general, a given two‐dimensional inhomogeneous potential V(x,y) does not allow for the creation of homogeneous families of orbits. Yet, depending on the case at hand, if the given potential satisfies certain conditions, this potential is compatible either with one (or two) monoparametric homogeneous families of orbits or at most with five such familes. The orbits are then found on the grounds of the given potential.
Interacting Galaxies — the X‐ray View
Authors: Hasinger G. , Fischer J.‐U. , Schwope A. D. , Boller T. , Trümper J. , Voges W.
Published: July 2007

We have selected a complete, flux‐limited sample of bright point‐like sources with absorbed X‐ray spectra from the ROSAT All‐Sky survey, the ROSAT Hard Survey (RHS). The sample is drawn from the high‐galactic latitude sky, |bII| > ±30°, and avoids the general direction of the Magellanic Clouds and the Virgo Cluster. It comprises a total of 182 objects of which 118 were previosly catalogued objects and 64 were new AGN candidates. Through optical follow‐up studies at La Silla, Calar Alto and the 6m Zelentchuk telescope we could identify 56 of the new objects, thus achieving a spectrscopic completeness of 96% of the sample. The selection strategy turned out to be extremely useful. Out of the new identifications, 84% are indeed active galaxies or emission line galaxies. While 14 objects are new BL Lac candidates 33 of the new AGN are Seyfert galaxies with a redshift distribution in the range 0.021–0.63, peaking at around 0.06, i.e. relatively local. Surprisingly, about 40% of the X‐ray selected Seyfert galaxies seem to reside in interacting systems. With smaller selection uncertainties this fraction exceeds the number of paired galaxies in optically selected samples and therefore gives strong support to the idea that AGN activity is triggered by interaction.
The number density of main‐belt asteroids
Authors: Lagerkvist C.‐I. , Lagerros J. S. V.
Published: July 2007

In this paper we have studied how the number density of asteroids varies as a function of the mean distance from the sun.
X‐ray Surveys Workshop
Authors: Hasinger G. , White N. E.
Published: July 2007

To mark the occasions of the 35th anniversary of the birth of X‐ray astronomy on June 18, 1962, and the 7th anniversary of the first light of ROSAT on June 16, 1990, the Astrophysikalisches Institut Potsdam (AIP) and the NASA Goddard Space Flight Center X‐ray Astrophysics Branch cosponsored a workshop entitled “X‐ray Surveys”.
Correlations of large scale X‐ray and radio surveys
Authors: Brinkmann W. , Siebert J.
Published: July 2007

A brief review is given of the study of radio‐loud AGN from the ROSAT Survey. Some general results as well as specific questions occuring in correlations of two large data bases are discussed.
Sky surveys with ASCA — Deep Sky Survey
Authors: Ogasaka Y. , Kii T. , Ueda Y. , Takahashi T. , Inoue H. , Ishisaki Y. , Ohta K. , Yamada T: , Makishima K. , Miyaji T. , Hasinger G.
Published: July 2007

ASCA Deep Sky Survey (DSS) is aimed to investigate the constituents of the CXB in 2–10 keV band, by faint source survey observations reaching to the source confusion limit of ASCA X‐Ray Telescopes. So far, 0.29 deg2 sky regions were systematically studied and about 40% of the CXB intensity was resolved into discrete sources. In this paper, we present the latest results on the number‐flux relation (LongN‐LogS) and spectrum properties of faint X‐ray sources.
ASCA observations of clusters of galaxies
Authors: Ikebe Y.
Published: July 2007

Some results from ASCA observations of clusters of galaxies are reviewed.
Astro‐E Mission and the X‐ray survey
Authors: Takahashi T. , Inoue H. , Ogawara Y.
Published: July 2007

The fifth Japaniese X‐ray astronomy satellite, Astro‐E, following Hakucho, Tenma, Ginga, and ASCA is scheduled for launch in the year 2000 by the Institute of Space and Astronautical Science (ISAS) with an M‐V rocket. The satellite will be put into an approximately circular orbit with an altitude of ∽550 km and an inclination of ∽31°. There will be three experiments on board Astro‐E: an X‐ray micro‐calorimeter array, four X‐ray CCDs and a hard X‐ray detector. All three experiments combined, Astro‐E will become a spectrometer facility covering a wide energy band from 0.5 keV to 600 keV.
Identification of new low‐mass members of the Alpha Persei open cluster by ROSAT. I
Authors: Prosser C. F. , Randich S.
Published: July 2007

Following the work of Randich et al. (1996) involving a ROSAT raster scan survey of the α Persei open cluster, we present here the results of a photometric/spectroscopic program examining the possible optical counterparts to a group of 73 X‐ray sources in the raster survey which were not matched to catalogued stars. Of the 73 sources investigated, ∽ 40 have an optical counterpart with photometry acceptable for cluster membership and ∽ 20 of these also have radial velocities consistent with membership. We discuss the X‐ray properties of these potential new members and why they may not have been identified in earlier membership surveys of this cluster.
Recent developments in the site‐specific immobilization of proteins onto solid supports
Authors: Camarero Julio A.
Published: July 2007

Immobilization of proteins onto surfaces is of great importance in numerous applications, including protein analysis, drug screening, and medical diagnostics, among others. The success of all these technologies relies on the immobilization technique employed to attach a protein to the corresponding surface. Non‐specific physical adsorption or chemical cross‐linking with appropriate surfaces results in the immobilization of the protein in random orientations. Site‐specific covalent attachment, on the other hand, leads to molecules being arranged in a definite, orderly fashion and allows the use of spacers and linkers to help minimize steric hindrances between the protein and the surface. The present work reviews the latest chemical and biochemical developments for the site‐specific covalent attachment of proteins onto solid supports. © 2007 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 90: 450–458, 2008.

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Presentation of functional organophosphorus hydrolase fusions on the surface of Escherichia coli by the AIDA‐I autotransporter pathway
Authors: Li Chaokun , Zhu Yaran , Benz Inga , Schmidt M. Alexander , Chen Wilfred , Mulchandani Ashok , Qiao Chuanling
Published: July 2007

We report, the surface presentation of organophosphorus hydrolase (OPH) and green fluorescent protein (GFP) fusions by employing the adhesin‐involved‐in‐diffuse‐adherence (AIDA‐I) translocator domain as a transporter and anchoring motif. The surface location of the OPH–GFP fusion protein was confirmed by immunofluorescence microscopy, and protease accessibility, followed by Western blotting analysis. The investigation of growth kinetics and stability of resting cultures showed that the presence of the AIDA‐I translocator domain in the outer membrane neither inhibits cell growth nor affects cell viability. Furthermore, the surface‐exposed OPH–GFP was shown to have enzymatic activity and a functional fluorescence moiety. These results suggest that AIDA‐I autotransporter is a useful tool to present heterologous macromolecule passenger proteins on the bacterial surface. Our strategy of linking GFP to OPH and the possibility to employ various bacterial species as host has enormous potential for enhancing field use. Biotechnol. Bioeng. 2008;99: 485–490. © 2007 Wiley Periodicals, Inc.
Target‐driven liquid animation with interfacial discontinuities
Authors: Shin Seung‐Ho , Kim Chang‐Hun
Published: July 2007

We propose a novel method of controlling a multi‐phase fluid so that it flows into a target shape in a natural way. To preserve the sharp detail of the target shape, we represent it as an implicit function and construct the level‐set of that function. Previous approaches add the target‐driven control force as an external term, which then becomes attenuated during the velocity projection step, making the convergence process unstable and causing sharp detail to be lost from the target shape. But we calculate the force on the fluid from the pressure discontinuity at the interface between phases, and integrate the control force into the projection step so as to preserve its effect. The control force is calculated using an enhanced version of the ghost fluid method (GFM), which guarantees that the fluid flows from the source shape and converges into the target shape, while achieving a more natural animation than other approaches. Our control force is merged during the projection step avoiding the need for a post‐optimization process to eliminate divergence at the liquid interface. This makes our method easy to implement using existing fluid engines and it incurs little computational overhead. Experimental results show the accuracy and robustness of this technique. Copyright © 2007 John Wiley & Sons, Ltd.
Metal–Metal Electronic Coupling in syn and anti Stereoisomers of Mixed‐Valent (FeCp)2‐, (RhL2)2‐, and (FeCp)(RhL2)‐as‐Indacenediide Ions
Authors: Santi Saverio , Orian Laura , Durante Christian , Bencze Eva Zsuzsanna , Bisello Annalisa , Donoli Alessandro , Ceccon Alberto , Benetollo Franco , Crociani Laura
Published: July 2007

The extent of metal–metal electronic coupling was quantified for a series of syn and anti stereoisomers of (FeCp)2‐, (RhL2)2‐ and (FeCp)(RhL2)‐ (L2=1,5‐cyclooctadiene (cod), L=CO) as‐indacenediide mixed‐valent ions by spectroelectrochemical and DFT studies. The effect of the syn/anti orientation of the metal units with respect to the planar aromatic ligand indicates that electron transfer occurs through the bridge rather than through space. The nature of the metal was found to be crucial: while homobimetallic diiron species are localised valence‐trapped ions (Class II), the dirhodium analogues are almost delocalised mixed‐valent ions (borderline and Class III). Finally, despite their redox asymmetry, even in the heterobimetallic iron–rhodium as‐indacenediide complexes, strong metal–metal coupling is present. In fact, oxidation of the iron centre is accompanied by electron transfer from rhodium to iron and formation of a reactive 17‐electron rhodium site. syn and anti Fe–Rh as‐indacenediide complexes are rare examples of heterobimetallic systems which can be classified as borderline Class II/Class III species.
N‐Heterocyclic Carbene and Phosphine Ruthenium Indenylidene Precatalysts: A Comparative Study in Olefin Metathesis
Authors: Clavier Hervé , Nolan Steven P.
Published: July 2007

Kinetic studies on ring‐closing metathesis of unhindered and hindered substrates using phosphine and N‐heterocyclic carbene (NHC)‐containing ruthenium‐indenylidene complexes (first and second generation precatalysts, respectively) have been carried out. These studies reveal an appealing difference, between the phosphine and NHC‐containing catalysts, associated with a distinctive rate‐determining step in the reaction mechanism. These catalysts have been compared with the benzylidene generation catalysts and their respective representative substrates. Finally, the reaction scope of the two most interesting precatalysts, complexes that contain tricyclohexylphosphine and 1,3‐bis(2,4,6‐trimethylphenyl)imidazol‐2‐ylidene (SIMes), has been investigated for the ring‐closing and enyne metathesis for a large range of olefins. Owing to their high thermal stability, the SIMes‐based indenylidene complexes were more efficient than their benzylidene analogues in the ring‐closing metathesis of tetrasubstituted dienes. Importantly, none of the indenylidene precatalysts were found to be the most efficient for all of the substrates, indeed, a complementary complex‐to‐substrate activity relationship was observed.
Bis‐alkynyl Diruthenium Compounds with Built‐in Electronic Asymmetry: Toward an Organometallic Aviram–Ratner Diode
Authors: Ying Jie‐Wen , Cordova Antoinette , Ren Tony Y. , Xu Guo‐Lin , Ren Tong
Published: July 2007

Conditions to prepare trans‐[Ru2(dmba)4(CCAr)2] from [Ru2(dmba)4(NO3)2] (DMBA=N,N′‐dimethylbenzamidinate) and HCCAr were optimized; Et2NH was found to be the most effective among a number of weak bases in facilitating the product formation. Furthermore, a series of unsymmetric trans‐[(ArCC)Ru2(dmba)4(CCAr′)] compounds were prepared under optimized conditions, in which one or both of Ar and Ar′ are donor (NMe2)‐/acceptor (NO2)‐substituted phenyls. While the X‐ray crystallographic studies revealed a minimal structural effect upon donor/acceptor substitution, voltammetric measurements indicated a significant influence of substituents on the energy level of frontier orbitals. In particular, placing a donor and an acceptor on the opposite ends of trans‐[(ArCC)Ru2(dmba)4(CCAr′)] moiety results in an energetic alignment of frontier orbitals that favors a directional electron flow, a necessary condition for unimolecular rectification.
Confocal Microscopy Imaging of Electrochemiluminescence at Double Band Microelectrode Assemblies: Numerical Solution of the Inverse Optical Problem
Authors: Amatore Christian , Oleinick Alexander , Klymenko Oleksiy V. , Thouin Laurent , Servant Laurent , Svir Irina
Published: July 2007

A realistic theoretical model describing the outcome of confocal microscopic imaging of electrochemiluminescence (ECL) light emission is derived for a two parallel band microelectrodes assembly operated under steady state. The model takes into account the experimental distortions ensuing from a) the specific finite shape of the sampling volume in confocal microscopy, b) the light arising directly from out‐of‐focus area but transmitted through the microscope diaphragm or c) transmitted after reflection from the polished platinum band electrodes. The model is based on a detailed optical, physico‐mathematical and numerical analysis of the problem at hand, and on simulations of the concentration distribution of the species giving rise to the ECL generation. Its outcome allows the reconstruction of the real spatial distribution of ECL light emission based on the confocal microscopy measurements upon correcting for the effect of experimental distortions using numerical fitting procedure.
Optimization of control parameters of cadmium zinc telluride Bridgman single crystal growth
Authors: Juncheng Liu , Dejie Song , Hongying Zhang , Shenqiu Zhai
Published: July 2007

The temperature gradient within a furnace chamber and the crucible pull rate are the key control parameters for cadmium zinc telluride Bridgman single crystal growth. Their effects on the heat and mass transfer in front of the solid‐liquid interface and the solute segregation in the grown crystal were investigated with numerical modeling. With an increase of the temperature gradient, the convection intensity in the melt in front of the solid‐liquid interface increases almost proportionally to the temperature gradient. The interface concavity decreases rapidly at faster crucible pull rates, while it increases at slow pull rates. Moreover, the solute concentration gradient in the melt in front of the solid‐liquid interface decreases significantly, as does the radial solute segregation in the grown crystal. In general, a decrease of the pull rate leads to a strong decrease of the concavity of the solid‐liquid interface and of the radial solute segregation in the grown crystal, while the axial solute segregation in the grown crystal increases slightly. A combination of a low crucible pull rate with a medium temperature gradient within the furnace chamber will make the radial solute segregation of the grown crystal vanish. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Temperature field design, process analysis and control of SAPMAC method for the growth of large size sapphire crystals
Authors: Xu C. H. , Zhang M. F. , Meng S. H. , Han J. C. , Wang G. G. , Zuo H. B.
Published: July 2007

In this paper, the relationship between quality of sapphire crystal and growing parameters of SAPMAC (Sapphire growth technique with micro‐pulling and shoulder‐expanding at cooled center) method was discussed. Optimized temperature distribution and technique control were proposed by theoretical analysis, numerical simulation computation and experimental validation to obtain large size sapphire crystals. For a‐axis crystallized direction, with 1.0‐5.0mm/h growth velocity and 10‐30K/h temperature decreasing speed, large sapphire single crystal (∅︁240mm×210mm, 27.5kg) having high optical quality was successfully grown. The absorption spectrum of standard samples was measured as well. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synthesis and thermal, phase transition and FTIR spectral characterization of tetraethylammonium tetrachlorocuprate (II) crystals
Authors: Amirthaganesan G. , Kandhaswamy M. A.
Published: July 2007

Single crystals of tetraethylammonium tetrachlorocuprate (II), [N(C2H5)4]2CuCl4, were grown by slow evaporation method at room temperature. The crystals were characterized through powder XRD, thermogravimetric (TG‐DTA), low temperature differential scanning calorimetric (DSC) studies and FTIR spectroscopy. While the powder XRD pattern of the compound shows sharp Bragg peaks confirming the crystallinity of the compound, the TG‐DTA studies confirm formation of the compound in the stoichiometric ratio. The thermal anomalies observed in DSC curve at ‐120°C in the heating cycle and around ‐30°C in the cooling cycle indicate a first order phase transition. The phase transition was predicted to be associated with the ordering of CuCl42‐ and successive long range orientation of [N(C2H5)4]+ ions which are disordered at high temperatures. The cationic [N(C2H5)4]+ plays a role in phase transitions at low temperatures. The sharp exothermic peak observed in high temperature DSC indicates a structural phase transition when [N(C2H5)4]CuCl3 is formed on heating the compound. The FTIR spectra of the compound characterize the various chemical bonding and water molecules adsorbed in the compound. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Gesamtstrahlung des stationären und impulsüberlagerten Argon‐Hochtemperaturbogens
Authors: Neumann Werner
Published: July 2007

Die Gesamtstrahlungsleistung eines Argon‐Hochtemperaturbogens wird als Funktion der Bogenleistung im absoluten Maße bestimmt. Ferner wird die Gesamtstrahlungsenergie gemessen, die zusätzlich abgestrahlt wird, wenn dem stationären Bogenstrom ein Impulsstrom, der aus einer Kondensatorbatterie gespeist wird, überlagert wird. Diese Strahlungsenergie wird als Funktion der im Bogen umgesetzten gepulsten elektrischen Energie, die mit einem ballistischen Wattsekundenmesser gemessen wurde, in ein Diagramm eingetragen. Ergänzend wird die Bogencharakteristik nach. großen Stromstärken fortgesetzt, und ferner wird der radiale Temperaturverlauf im stationären Bogen im Abstand von 3 mm vor der Kathode bei einer Bogenstromstärke von 180 A angegeben.
Über den elektrischen Durchschlag von Argon unter hohem Druck
Authors: List Gunther
Published: July 2007

Bei Durchschlagsfeldstärken über 105 V/cm werden in komprimierten Gasen Abweichungen vom Paschen‐Gesetz beobachtet.

Es wurden die Durchschlagsspannungen von Argon bei Drücken bis zu 300 at und bei Verwendung verschiedener Elektrodenmetalle gemessen. Die Streuung der Durchschlagspannung wird durch eine Konstante c charakterisiert, die vom Elektrodenmaterial, den Eigenschaften der Kathodenoberfläche und dem Quotienten aus Durchschlagsfeldstärke und Gasdruck abhängt.

Der Durchschlag bei hohem Druck wird als ein Feldemissionsdurchschlag erklärt, wobei die erforderliche Feldstärke durch Anlagerung positiver Gasionen an die oxydierte Kathodenoberfläche erzeugt wird. Mit der Aufladung der Kathodenoberfläche steht ein Ladungsausgleich infolge der Leitfähigkeit der Oxydschicht in Konkurrenz. Beide Prozesse zusammen erklären die Größe der Streukonstanten c. Aus dem Gleichgewicht beider Prozesse wird eine Bedingung für die statische Durchschlagspannung abgeleitet.
Theorie der Schichtungswellen in Niederdruck‐Gasentladungen
Authors: Wojaczek Karl
Published: July 2007

Die in der positiven Säule der Niederdruck‐Gasentladung im Übergangsregime durch lokale, impulsförmige Störungen erzeugbaren Schichtungswellen werden als Wellenpakete laufender Schichten nicht verschwindenden Instabilitätsinkrements aufgefaßt. Sind das Dispersions‐ und das Amplifikationsverhalten stationärer laufender Schichten bekannt, so lassen sich so‐wohl die Kenndaten der Einhüllenden als auch die Kenndaten der Einzelschichten innerhalb der Schichtungswelle bezüglich ihrer Orts‐ und Zeitabhängigkeit vollständig berechnen.

Die in der Peakárekschen Theorie der Schichtungswelle bei Berücksichtigung von Stufenprozessen auftretenden Zeitparameter können in der Regel so bestimmt werden, daß die Ausbreitungsgeschwindigkeit und die Halbwertsbreite der Schichtungswelle mit den von der Dispersionstheorie geforderten Werten übereinstimmen. Jedoch ergeben die von beiden Theorien gefundenen Ausdrücke für die Asymmetrie der Schichtungswelle unterschiedliche Werte.
Der Zusammenhang zwischen stationär angeregten laufenden Schichten und den Schichtungswellen in Niederdruckentladungen
Authors: Novák Miloš , Wojaczek Karl
Published: July 2007

In einer Neon‐Niederdruckentladung im Puppschen Übergangsbereich wurden sowohl stationäre laufende Schichten als auch unter den gleichen Entladungsbedingungen Schichtungswellen angeregt. Die direkt gemessenen Kenndaten der Schichtungswellen stimmen gut mit den Werten überein, die sich mit Hilfe der Dispersionstheorie aus dem Frequenzgang von Schichtweite und Amplifikation stationärer laufender Schichten errechnen lassen. Demnach kann die der Dispersionstheorie zugrunde liegende Auffassung der Schichtungswelle als eines Wellenpaketes laufender Schichten auch als experimentell gut begründet angesehen werden.
Bestimmung des absoluten Strahlungsanteils von Hochdruckbögen in schweren Edelgasen
Authors: Neumann W.
Published: July 2007

Die Gesamtstrahlung von in zylindrischen Lampen brennenden wandstabilisierten Hochdruckbögen in den schweren Edelgasen Argon, Krypton und Xenon wurde gemessen und auf die in der Bogensäule umgesetzte elektrische Leistung bezogen. Die asymptotischen Werte der Strahlungsausbeute, die für große Bogenleistungen gelten, wurden zu 0,88 (Xenon), 0,72 (Krypton) und 0,52 (Argon) bestimmt. Diese Werte werden mit bisher aus der Literatur bekannten Werten verglichen.