@inproceedings{MassaPrinjaFullerton2007,
  author    = {Massa, D. L. and Prinja, R. K. and Fullerton, A. W.},
  title     = {The effects of clumping on wind line variability},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18095},
  year      = {2007},
  abstract  = {We review the effects of clumping on the profiles of resonance doublets. By allowing the ratio of the doublet oscillator strenghts to be a free parameter, we demonstrate that doublet profiles contain more information than is normally utilized. In clumped (or porous) winds, this ratio can lies between unity and the ratio of the f-values, and can change as a function of velocity and time, depending on the fraction of the stellar disk that is covered by material moving at a particular velocity at a given moment. Using these insights, we present the results of SEI modeling of a sample of B supergiants, ζ Pup and a time series for a star whose terminal velocity is low enough to make the components of its Si VIλλ1400 independent. These results are interpreted within the framewrok of the Oskinova et al. (2007) model, and demonstrate how the doublet profiles can be used to extract infromation about wind structure.},
  language  = {en}
}
@inproceedings{LeuteneggerCohenKahnetal.2007,
  author    = {Leutenegger, M. A. and Cohen, David H. and Kahn, S. M. and Owocki, S. P. and Paerels, F. B. S.},
  title     = {Resonance scattering in the X-ray emission lines profiles of ζ Puppis},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18085},
  year      = {2007},
  abstract  = {We present XMM-Newton Reflection Grating Spectrometer observations of pairs of X-ray emission line profiles from the O star ζ Pup that originate from the same He-like ion. The two profiles in each pair have different shapes and cannot both be consistently fit by models assuming the same wind parameters. We show that the differences in profile shape can be accounted for in a model including the effects of resonance scattering, which affects the resonance line in the pair but not the intercombination line. This implies that resonance scattering is also important in single resonance lines, where its effect is difficult to distinguish from a low effective continuum optical depth in the wind. Thus, resonance scattering may help reconcile X-ray line profile shapes with literature mass-loss rates.},
  language  = {en}
}
@inproceedings{SchnerrHenrichs2007,
  author    = {Schnerr, R. S. and Henrichs, H. F.},
  title     = {Magnetic fields and wind variability in massive stars},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18075},
  year      = {2007},
  abstract  = {This paper describes the thesis work of Schnerr (2007) entitled "Magnetic fields and mass loss in massive stars", which aimed at a better understanding of the impact of magnetic fields on the winds of massive stars.},
  language  = {en}
}
@inproceedings{IgnaceGayley2007,
  author    = {Ignace, R. and Gayley, K. G.},
  title     = {Circumstellar Magnetic Field Diagnostics from Line Polarization},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18066},
  year      = {2007},
  language  = {en}
}
@inproceedings{CassinelliIgnaceWaldronetal.2007,
  author    = {Cassinelli, Joseph P. and Ignace, R. and Waldron, W. and Cho, J. and Murphy, N. and Lazarian, A.},
  title     = {X-ray line emission produced in clump bow shocks},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18057},
  year      = {2007},
  abstract  = {We summarize Chandra observations of the emission line profiles from 17 OB stars. The lines tend to be broad and unshifted. The forbidden/intercombination line ratios arising from Helium-like ions provide radial distance information for the X-ray emission sources, while the H-like to He-like line ratios provide X-ray temperatures, and thus also source temperature versus radius distributions. OB stars usually show power law differential emission measure distributions versus temperature. In models of bow shocks, we find a power law differential emission measure, a wide range of ion stages, and the bow shock flow around the clumps provides transverse velocities comparable to HWHM values. We find that the bow shock results for the line profile properties, consistent with the observations of X-ray line emission for a broad range of OB star properties.},
  language  = {en}
}
@inproceedings{Vink2007,
  author    = {Vink, J. S.},
  title     = {Discussion: Hydrodynamic modeling},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18046},
  year      = {2007},
  language  = {en}
}
@inproceedings{Runacres2007,
  author    = {Runacres, M. C.},
  title     = {Hydrodynamical models of clumping beyond 50 R∗},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18030},
  year      = {2007},
  abstract  = {We present one-dimensional, time-dependent models of the clumps generated by the linedeshadowing instability. In order to follow the clumps out to distances of more than 1000 R∗, we use an efficient moving-box technique. We show that, within the approximations, the wind can remain clumped well into the formation region of the radio continuum.},
  language  = {en}
}
@inproceedings{WalterZuritaHerasLeyder2007,
  author    = {Walter, R. and Zurita-Heras, J. and Leyder, J.-C.},
  title     = {Probing clumpy stellar winds with a neutron star},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18024},
  year      = {2007},
  abstract  = {INTEGRAL tripled the number of super-giant high-mass X-ray binaries (sgHMXB) known in the Galaxy by revealing absorbed and fast transient (SFXT) systems. Quantitative constraints on the wind clumping of massive stars can be obtained from the study of the hard X-ray variability of SFXT. A large fraction of the hard X-ray emission is emitted in the form of flares with a typical duration of 3 ksec, frequency of 7 days and luminosity of \$10^{36}\$ erg/s. Such flares are most probably emitted by the interaction of a compact object orbiting at \$\sim10~R_*\$ with wind clumps (\$10^{22 ... 23}\$ g) representing a large fraction of the stellar mass-loss rate. The density ratio between the clumps and the inter-clump medium is \$10^{2 ... 4}\$. The parameters of the clumps and of the inter-clump medium, derived from the SFXT flaring behavior, are in good agreement with macro-clumping scenario and line-driven instability simulations. SFXT are likely to have larger orbital radius than classical sgHMXB.},
  language  = {en}
}
@inproceedings{udDoula2007,
  author    = {ud-Doula, A.},
  title     = {Large-scale wind structure due to magnetic fields},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18010},
  year      = {2007},
  abstract  = {Magnetic fields influence the dynamics of hot-star winds and create large scale structure. Based on numerical magnetohydrodynamic (MHD) simulations, we model the wind of θ¹ Ori C, and then use the SEI method to compute synthetic line profiles for a range of viewing angles as function of rotational phase. The resulting dynamic spectrum for a moderately strong line shows a distinct modulation, but with a phase that seems at odds with available observations.},
  language  = {en}
}
@inproceedings{Puls2007,
  author    = {Puls, Joachim},
  title     = {Discussion : X-rays},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18000},
  year      = {2007},
  abstract  = {Clumping in hot-star winds : proceedings of an international workshop held in Potsdam, Germany, 18. - 22. June 2007},
  language  = {en}
}
@inproceedings{Owocki2007,
  author    = {Owocki, S. P.},
  title     = {Dynamical simulation of the "velocity-porosity" reduction in observed strength of stellar wind lines},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17992},
  year      = {2007},
  abstract  = {I use dynamical simulations of the line-driven instability to examine the potential role of the resulting flow structure in reducing the observed strength of wind absorption lines. Instead of the porosity length formalism used to model effects on continuum absorption, I suggest reductions in line strength can be better characterized in terms of a velocity clumping factor that is insensitive to spatial scales. Examples of dynamic spectra computed directly from instability simulations do exhibit a net reduction in absorption, but only at a modest 10-20\% level that is well short of the ca. factor 10 required by recent analyses of PV lines.},
  language  = {en}
}
@inproceedings{Sonneborn2007,
  author    = {Sonneborn, G.},
  title     = {Imaging and spectroscopy with the James Webb Space Telescope},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17983},
  year      = {2007},
  abstract  = {The James Webb Space Telescope (JWST) is a large, infrared-optimized space telescope scheduled for launch in 2013. JWST will find the first stars and galaxies that formed in the early universe, connecting the Big Bang to our own Milky Way galaxy. JWST will peer through dusty clouds to see stars forming planetary systems, connecting the MilkyWay to our own Solar System. JWST's instruments are designed to work primarily in the infrared range of 1 - 28 μm, with some capability in the visible range. JWST will have a large mirror, 6.5 m in diameter, and will be diffraction-limited at 2 μm (0.1 arcsec resolution). JWST will be placed in an L2 orbit about 1.5 million km from the Earth. The instruments will provide imaging, coronography, and multi-object and integral-field spectroscopy across the 1 - 28 μm wavelength range. The breakthrough capabilities of JWST will enable new studies of massive star winds from the Milky Way to the early universe.},
  language  = {en}
}
@inproceedings{FeldmeierHamannRaetzeletal.2007,
  author    = {Feldmeier, Achim and Hamann, Wolf-Rainer and R{\"a}tzel, D. and Oskinova, Lida},
  title     = {Hydrodynamic simulations of clumps},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17975},
  year      = {2007},
  abstract  = {Clumps in hot star winds can originate from shock compression due to the line driven instability. One-dimensional hydrodynamic simulations reveal a radial wind structure consisting of highly compressed shells separated by voids, and colliding with fast clouds. Two-dimensional simulations are still largely missing, despite first attempts. Clumpiness dramatically affects the radiative transfer and thus all wind diagnostics in the UV, optical, and in X-rays. The microturbulence approximation applied hitherto is currently superseded by a more sophisticated radiative transfer in stochastic media. Besides clumps, i.e. jumps in the density stratification, so-called kinks in the velocity law, i.e. jumps in dv/dr, play an eminent role in hot star winds. Kinks are a new type of radiative-acoustic shock, and propagate at super-Abbottic speed.},
  language  = {en}
}
@inproceedings{MoffatHillierHamannetal.2007,
  author    = {Moffat, Anthony F. J. and Hillier, D. J. and Hamann, Wolf-Rainer and Owocki, S. P.},
  title     = {General Discussion},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17953},
  year      = {2007},
  abstract  = {Clumping in hot-star winds : proceedings of an international workshop held in Potsdam, Germany, 18. - 22. June 2007},
  language  = {en}
}
@inproceedings{KrtičkaPulsKubat2007,
  author    = {Krtička, Jiri and Puls, Joachim and Kub{\´a}t, Jiř{\´i}},
  title     = {The influence of clumping on predicted O star wind parameters},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17969},
  year      = {2007},
  abstract  = {We study the influence of clumping on the predicted wind structure of O-type stars. For this purpose we artificially include clumping into our stationary wind models. When the clumps are assumed to be optically thin, the radiative line force increases compared to corresponding unclumped models, with a similar effect on either the mass-loss rate or the terminal velocity (depending on the onset of clumping). Optically thick clumps, alternatively, might be able to decrease the radiative force.},
  language  = {en}
}
@inproceedings{VinkBenagliaDaviesetal.2007,
  author    = {Vink, J. S. and Benaglia, P. and Davies, B. and de Koter, A. and Oudmaijer, R. D.},
  title     = {Advances in mass-loss predictions},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17948},
  year      = {2007},
  abstract  = {We present the results of Monte Carlo mass-loss predictions for massive stars covering a wide range of stellar parameters. We critically test our predictions against a range of observed massloss rates - in light of the recent discussions on wind clumping. We also present a model to compute the clumping-induced polarimetric variability of hot stars and we compare this with observations of Luminous Blue Variables, for which polarimetric variability is larger than for O and Wolf-Rayet stars. Luminous Blue Variables comprise an ideal testbed for studies of wind clumping and wind geometry, as well as for wind strength calculations, and we propose they may be direct supernova progenitors.},
  language  = {en}
}
@inproceedings{DaviesVinkOudmaijer2007,
  author    = {Davies, B. and Vink, J. S. and Oudmaijer, R. D.},
  title     = {Modelling the polarimetric variability of hot stars},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17939},
  year      = {2007},
  abstract  = {Many hot stars exhibit stochastic polarimetric variability, thought to arise from clumping low in the wind. Here we investigate the wind properties required to reproduce this variability using analytic models, with particular emphasis on Luminous Blue Variables. We find that the winds must be highly structured, consisting of a large number of optically-thin clumps; while we find that the overall level of polarization should scale with mass-loss rate - consistent with observations of LBVs. The models also predict variability on very short timescales, which is supported by the results of a recent polarimetric monitoring campaign.},
  language  = {en}
}
@inproceedings{Graefener2007,
  author    = {Gr{\"a}fener, G.},
  title     = {Clumping in hydrodynamic atmosphere models},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17925},
  year      = {2007},
  abstract  = {We investigate the effect of wind clumping on the dynamics of Wolf-Rayet winds, by means of the Potsdam Wolf-Rayet (PoWR) hydrodynamic atmosphere models. In the limit of microclumping the radiative acceleration is generally enhanced. We examine the reasons for this effect and show that the resulting wind structure depends critically on the assumed radial dependence of the clumping factor D(r). The observed terminal wind velocities for WR stars imply that D(r) increases to very large values in the outer part of the wind, in agreement with the assumption of detached expanding shells.},
  language  = {en}
}
@inproceedings{Fullerton2007,
  author    = {Fullerton, A. W.},
  title     = {Discussion: Spectral modeling},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17917},
  year      = {2007},
  language  = {en}
}
@inproceedings{Hillier2007,
  author    = {Hillier, D. J.},
  title     = {On the influence of clumping on O and Wolf-Rayet spectra},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17903},
  year      = {2007},
  abstract  = {Overwhelming observational and theoretical evidence suggests that the winds of massive stars are highly clumped. We briefly discuss the influence of clumping on model diagnostics and the difficulties of allowing for the influence of clumping on model spectra. Because of its simplicity, and because of computational ease, most spectroscopic analyses incorporate clumping using the volume filling factor. The biases introduced by this approach are uncertain. To investigate alternative clumping models, and to help determine the validity of parameters derived using the volume filling factor method, we discuss results derived using an alternative model in which we assume that the wind is composed of optically thick shells.},
  language  = {en}
}
@inproceedings{IpingSonnebornMassaetal.2007,
  author    = {Iping, R.C. and Sonneborn, G. and Massa, D.L. and Gies, D. and Williams, Simon E.},
  title     = {Far-ultraviolet spectroscopy of O+O binaries in the Magellanic Clouds},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17896},
  year      = {2007},
  abstract  = {We report FUSE observations in 2005-2006 of three O-type, double-lined spectroscopic binaries in the Magellanic Clouds. The systems have very short periods (1.4-2.25 d), represent rare, young evolutionary stages of massive stars and binaries, and provide a unique glimpse at some of the most massive systems that form in dense clusters of massive stars. Improved orbit parameters, including revised masses, for LH54-425 are derived from new ctio spectroscopy. The systems are: LH54-425 in the LMC (O3V + O5V, P=2.25d, 62+37M⊙), J053441-693139 in the LMC (O2-3If+O6V, P=1.4 d, 41+27M⊙), and Hodge 53-47 in the SMC (O6V + O4-5IIIf, P=2.2 d, 24+14M⊙, where the O4 star appears to be less massive than the O6 star). Their short periods indicates that wind interaction and mass transfer are likely important factors in their evolution. The spectra provide quantitative and systematic studies of phase-dependent stellar wind properties, wind collision effects in O+O binaries at lower metallicities, improved radial velocity curves, and FUV spectro-photometric changes as a function of orbital phase.},
  language  = {en}
}
@inproceedings{SchnurrCrowther2007,
  author    = {Schnurr, O. and Crowther, P. A.},
  title     = {Mid-IR observations of WC stars, and the connection to wind clumping},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17884},
  year      = {2007},
  abstract  = {We present preliminary results of a tailored atmosphere analysis of six Galactic WC stars using UV, optical, and mid-infrared Spitzer IRS data. With these data, we are able to sample regions from 10 to 10³ stellar radii, thus to determine wind clumping in different parts of the wind. Ultimately, derived wind parameters will be used to accuratelymeasure neon abundances, and to so test predicted nuclear-reaction rates.},
  language  = {en}
}
@inproceedings{Townsend2007,
  author    = {Townsend, R. H. D.},
  title     = {Techniques for simulating radiative transfer through porous media},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17866},
  year      = {2007},
  abstract  = {In this contribution, I discuss some basic techniques that can be used to simulate radiative transfer through porous media. As specific examples, I consider scattering transfer through a clumped slab, and X-ray emission line formation in a clumped wind.},
  language  = {en}
}
@inproceedings{KubatSaad2007,
  author    = {Kub{\´a}t, Jiř{\´i} and Saad, S. M.},
  title     = {Moving absorption bumps in the spectra of Be stars},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17879},
  year      = {2007},
  abstract  = {Several Be binaries exhibit an absorption bump moving across the blue wing of hydrogen emission lines towards the line center. This bump is demonstrated for the case of two bright Be stars, κ Dra and 4 Her. It is not clear what is the reason for this travelling bump.},
  language  = {en}
}
@inproceedings{KustererNagelWerneretal.2007,
  author    = {Kusterer, D.-J. and Nagel, T. and Werner, K. and Feldmeier, Achim},
  title     = {Radiative transfer in CV disk winds},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17847},
  year      = {2007},
  abstract  = {Mass accretion onto compact objects through accretion disks is a common phenomenon in the universe. It is seen in all energy domains from active galactic nuclei through cataclysmic variables (CVs) to young stellar objects. Because CVs are fairly easy to observe, they provide an ideal opportunity to study accretion disks in great detail and thus help us to understand accretion also in other energy ranges. Mass accretion in these objects is often accompanied by mass outflow from the disks. This accretion disk wind, at least in CVs, is thought to be radiatively driven, similar to O star winds. WOMPAT, a 3-D Monte Carlo radiative transfer code for accretion disk winds of CVs is presented.},
  language  = {en}
}
@inproceedings{Lobel2007,
  author    = {Lobel, A.},
  title     = {Modeling DACs in UV lines of massive hot stars},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17856},
  year      = {2007},
  abstract  = {We apply the 3-dimensional radiative transport codeWind3D to 3D hydrodynamic models of Corotating Interaction Regions to fit the detailed variability of Discrete Absorption Components observed in Si iv UV resonance lines of HD 64760 (B0.5 Ib). We discuss important effects of the hydrodynamic input parameters on these large-scale equatorial wind structures that determine the detailed morphology of the DACs computed with 3D transfer. The best fit model reveals that the CIR in HD 64760 is produced by a source at the base of the wind that lags behind the stellar surface rotation. The non-corotating coherent wind structure is an extended density wave produced by a local increase of only 0.6\% in the smooth symmetric wind mass-loss rate.},
  language  = {en}
}
@inproceedings{HamannOskinovaFeldmeier2007,
  author    = {Hamann, Wolf-Rainer and Oskinova, Lida and Feldmeier, Achim},
  title     = {Spectrum formation in clumpy stellar winds},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17838},
  year      = {2007},
  abstract  = {Modeling expanding atmospheres is a difficult task because of the extreme non-LTE situation, the need to account for complex model atoms, especially for the iron-group elements with their millions of lines, and because of the supersonic expansion. Adequate codes have been developed e.g. by Hillier (CMFGEN), the Munich group (Puls, Pauldrach), and in Potsdam (PoWR code, Hamann et al.). While early work was based on the assumption of a smooth and homogeneous spherical stellar wind, the need to account for clumping became obvious about ten years ago. A relatively simple first-order clumping correction was readily implemented into the model codes. However, its simplifying assumptions are severe. Most importantly, the clumps are taken to be optically thin at all frequencies ("microclumping"). We discuss the consequences of this approximation and describe an approach to account for optically thick clumps ("macroclumping"). First results demonstrate that macroclumping can generally reduce the strength of spectral features, depending on their optical thickness. The recently reported discrepancy between the Hα diagnostic and the Pv resonance lines in O star spectra can be resolved without decreasing the mass-loss rates, when macroclumping is taken into account.},
  language  = {en}
}
@inproceedings{LiermannHamann2007,
  author    = {Liermann, A. and Hamann, Wolf-Rainer},
  title     = {Clumping in Galactic WN stars : a comparison of mass loss rates from UV/optical \& radio diagnostics},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17816},
  year      = {2007},
  abstract  = {The mass loss rates and other parameters for a large sample of Galactic WN stars have been revised by Hamann et al. (2006), using the most up-to date Potsdam Wolf-Rayet (PoWR) model atmospheres. For a sub-sample of these stars exist measurements of their radio free-free emission. After harmonizing the adopted distance and terminal wind velocities, we compare the mass loss rates obtained from the two diagnostics. The differences are discussed as a possible consequence of different clumping contrast in the line-forming and radio-emitting regions.},
  language  = {en}
}
@inproceedings{Massa2007,
  author    = {Massa, D. L.},
  title     = {Discussion: Spectroscopy and Mass-Loss Diagnostics},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17821},
  year      = {2007},
  language  = {en}
}
@inproceedings{UrbanejaKudritzkiPuls2007,
  author    = {Urbaneja, M. A. and Kudritzki, R.-P. and Puls, Joachim},
  title     = {Clumping in the winds of O-type CSPNs},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17801},
  year      = {2007},
  abstract  = {Recent studies of massive O-type stars present clear evidences of inhomogeneous and clumped winds. O-type (H-rich) central stars of planetary nebulae (CSPNs) are in some ways the low mass-low luminosity analogous of those massive stars. In this contribution, we present preliminary results of our on-going multi-wavelength (FUV, UV and optical) study of the winds of Galactic CSPNs. Particular emphasis will be given to the clumping factors derived by means of optical lines (Hα and Heii 4686) and "classic" FUV (and UV) lines.},
  language  = {en}
}
@inproceedings{Kholtygin2007,
  author    = {Kholtygin, A. F.},
  title     = {Wavelets for looking for clumping in the wind of OB stars},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17796},
  year      = {2007},
  abstract  = {Clumping in hot-star winds : proceedings of an international workshop held in Potsdam, Germany, 18. - 22. June 2007},
  language  = {en}
}
@inproceedings{PrinjaHodgesMassaetal.2007,
  author    = {Prinja, R. K. and Hodges, S. E. and Massa, D. L. and Fullerton, A. W. and Burnley, A. W.},
  title     = {Structure in the fast wind of NGC6543},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17788},
  year      = {2007},
  abstract  = {We exploit time-series \$FUSE\$ spectroscopy to {\it uniquely} probe spatial structure and clumping in the fast wind of the central star of the H-rich planetary nebula NGC~6543 (HD~164963). Episodic and recurrent optical depth enhancements are discovered in the P{\sc v} absorption troughs, with some evidence for a \$\sim\$ 0.17-day modulation time-scale. The characteristics of these features are essentially identical to the discrete absorption components' (DACs) commonly seen in the UV lines of massive OB stars, suggesting the temporal structures seen in NGC~6543 likely have a physical origin that is similar to that operating in massive, luminous stars. The mechanism for forming coherent perturbations in the outflows is therefore apparently operating equally in the radiation-pressure-driven winds of widely differing momenta (\$\mdot\$\$v_\infty\$\$R_\star^{0.5}\$) and flow times, as represented by OB stars and CSPN.},
  language  = {en}
}
@inproceedings{GrohHillierDamineli2007,
  author    = {Groh, J. H. and Hillier, D. J. and Damineli, A.},
  title     = {Mass-loss rate and clumping in LBV stars : the impact of time-dependent effects},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17773},
  year      = {2007},
  abstract  = {This paper outlines a newly-developed method to include the effects of time variability in the radiative transfer code CMFGEN. It is shown that the flow timescale is often large compared to the variability timescale of LBVs. Thus, time-dependent effects significantly change the velocity law and density structure of the wind, affecting the derivation of the mass-loss rate, volume filling factor, wind terminal velocity, and luminosity. The results of this work are directly applicable to all active LBVs in the Galaxy and in the LMC, such as AG Car, HR Car, S Dor and R 127, and could result in a revision of stellar and wind parameters. The massloss rate evolution of AG Car during the last 20 years is presented, highlighting the need for time-dependent models to correctly interpret the evolution of LBVs.},
  language  = {en}
}
@inproceedings{RaassenHuchtMilleretal.2007,
  author    = {Raassen, A. J. J. and Hucht, K. A. van der and Miller, N. A. and Cassinelli, Joseph P.},
  title     = {XMM-Newton observations of zeta Orionis (O9.7 Ib) : a collisional ionization equilibrium model},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17747},
  year      = {2007},
  abstract  = {We present the analysis of XMM-Newton observations of ζ Orionis. The analysis is based on fitting to the total spectrum as well as diagnostics of individual line.},
  language  = {en}
}
@inproceedings{Marchenko2007,
  author    = {Marchenko, S. V.},
  title     = {Wind inhomogeneities in low-Z environment : observations},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17769},
  year      = {2007},
  abstract  = {We discuss the results of time-resolved spectroscopy of three presumably single Population I Wolf-Rayet stars in the Small Magellanic Cloud, where the ambient metallicity is \$\sim 1/5 Z_\odot\$. We were able to detect and follow numerous small-scale wind-embedded inhomogeneities in all observed stars. The general properties of the moving features, such as their velocity dispersions, emissivities and average accelerations, closely match the corresponding characteristics of small-scale inhomogeneities in the winds of Galactic Wolf-Rayet stars.},
  language  = {en}
}
@inproceedings{KrausKubatKrtička2007,
  author    = {Kraus, M. and Kub{\´a}t, Jiř{\´i} and Krtička, Jiri},
  title     = {Wind emission of OB supergiants and the influence of clumping},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17757},
  year      = {2007},
  abstract  = {The influence of the wind to the total continuum of OB supergiants is discussed. For wind velocity distributions with β > 1.0, the wind can have strong influence to the total continuum emission, even at optical wavelengths. Comparing the continuum emission of clumped and unclumped winds, especially for stars with high β values, delivers flux differences of up to 30\% with maximum in the near-IR. Continuum observations at these wavelengths are therefore an ideal tool to discriminate between clumped and unclumped winds of OB supergiants.},
  language  = {en}
}
@inproceedings{ReyesIturbideVelazquezRosado2007,
  author    = {Reyes-Iturbide, J. and Vel{\´a}zquez, P. and Rosado, M.},
  title     = {3D numerical model for an asymmetrical superbubble},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17724},
  year      = {2007},
  abstract  = {Massive stars usually form groups such as OB associations. Their fast stellar winds sweep up collectively the surrounding insterstellar medium (ISM) to generate superbubbles. Observations suggest that superbubble evolution on the surrounding ISM can be very irregular. Numerical simulations considering these conditions could help to understand the evolution of these superbubbles and to clarify the dynamics of these objects as well as the difference between observed X-ray luminosities and the predicted ones by the standard model (Weaver et al. 1977).},
  language  = {en}
}
@inproceedings{deKoterVinkMuijres2007,
  author    = {de Koter, A. and Vink, J. S. and Muijres, L.},
  title     = {Constraints on wind clumping from the empirical mass-loss vs. metallicity relation for early-type stars},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17736},
  year      = {2007},
  abstract  = {We present the latest results on the observational dependence of the mass-loss rate in stellar winds of O and early-B stars on the metal content of their atmospheres, and compare these with predictions. Absolute empirical rates for the mass loss of stars brighter than 10\$^{5.2} L_{\odot}\$, based on H\$\alpha\$ and ultraviolet (UV) wind lines, are found to be about a factor of two higher than predictions. If this difference is attributed to inhomogeneities in the wind this would imply that luminous O and early-B stars have clumping factors in their H\$\alpha\$ and UV line forming regime of about a factor of 3--5. The investigated stars cover a metallicity range \$Z\$ from 0.2 to 1 \$Z_{\odot}\$. We find a hint towards smaller clumping factors for lower \$Z\$. The derived clumping factors, however, presuppose that clumping does not impact the predictions of the mass-loss rate. We discuss this assumption and explain how we intend to investigate its validity in more detail.},
  language  = {en}
}
@inproceedings{NajarroPulsHerreroetal.2007,
  author    = {Najarro, F. and Puls, Joachim and Herrero, A. and Hanson, M. M. and Mart{\´i}n-Pintado, J. and Hillier, D. J.},
  title     = {Tracking the Clumping in OB Stars from UV to radio},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17701},
  year      = {2007},
  abstract  = {We review different line and continua diagnostics from the UV to radio, which can be utilized to simultaneously constrain the clumping structure throughout the stellar wind of massive OB stars.},
  language  = {en}
}
@inproceedings{TodtHamannGraefener2007,
  author    = {Todt, Helge Tobias and Hamann, Wolf-Rainer and Gr{\"a}fener, G.},
  title     = {Clumping in [WC]-type Central Stars from electron-scattering line wings},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17711},
  year      = {2007},
  abstract  = {While there is strong evidence for clumping in the winds of massive hot stars, very little is known about clumping in the winds from Central Stars. We have checked [WC]-type CSPN winds for clumping by inspecting the electron-scattering line wings. At least for three stars we found indications for wind inhomogeneities.},
  language  = {en}
}
@inproceedings{StLouisMoffat2007,
  author    = {St-Louis, N. and Moffat, Anthony F. J.},
  title     = {Do clumping corrections increase with decreasing mass-loss rates?},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17696},
  year      = {2007},
  abstract  = {We report on new mass-loss rate estimates for O stars in six massive binaries using the amplitude of orbital-phase dependent, linear-polarimetric variability caused by electron scattering off free electrons in the winds. Our estimated mass-loss rates for luminous O stars are independent of clumping. They suggest similar clumping corrections as for WR stars and do not support the recently proposed reduction in mass-loss rates of O stars by one or two orders of magnitude.},
  language  = {en}
}
@inproceedings{VotrubaFeldmeierKubatetal.2007,
  author    = {Votruba, V. and Feldmeier, Achim and Kub{\´a}t, Jiř{\´i} and R{\"a}tzel, D.},
  title     = {Multicomponent stellar wind of hot stars},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17677},
  year      = {2007},
  abstract  = {We developed a time-dependent multicomponent hydrodynamical code for simulation of the stellar wind from hot stars and applied it to stars with high and low density winds.},
  language  = {en}
}
@inproceedings{PulsMarkovaNajarroetal.2007,
  author    = {Puls, Joachim and Markova, N. and Najarro, F. and Hanson, M. M.},
  title     = {Clumping in O-star winds},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17683},
  year      = {2007},
  abstract  = {We review various diagnostics of clumping in O-star winds, with special emphasis on its radial stratification. Implications and problems are discussed, and promising NIR methods are presented.},
  language  = {en}
}
@inproceedings{BouretLanzHillieretal.2007,
  author    = {Bouret, J.-C. and Lanz, T. and Hillier, D. J. and Foellmi, C.},
  title     = {Clumping in O-type Supergiants},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17662},
  year      = {2007},
  abstract  = {We have analyzed the spectra of seven Galactic O4 supergiants, with the NLTE wind code CMFGEN. For all stars, we have found that clumped wind models match well lines from different species spanning a wavelength range from FUV to optical, and remain consistent with Hα data. We have achieved an excellent match of the P V λλ1118, 1128 resonance doublet and N IV λ1718, as well as He II λ4686 suggesting that our physical description of clumping is adequate. We find very small volume filling factors and that clumping starts deep in the wind, near the sonic point. The most crucial consequence of our analysis is that the mass loss rates of O stars need to be revised downward significantly, by a factor of 3 and more compared to those obtained from smooth-wind models.},
  language  = {en}
}
@inproceedings{Smith2007,
  author    = {Smith, Nathan},
  title     = {Independent signs of lower mass-loss rates for O-type stars},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17659},
  year      = {2007},
  abstract  = {I discuss observational evidence - independent of the direct spectral diagnostics of stellar winds themselves - suggesting that mass-loss rates for O stars need to be revised downward by roughly a factor of three or more, in line with recent observed mass-loss rates for clumped winds. These independent constraints include the large observed mass-loss rates in LBV eruptions, the large masses of evolved massive stars like LBVs and WNH stars, WR stars in lower metallicity environments, observed rotation rates of massive stars at different metallicity, supernovae that seem to defy expectations of high mass-loss rates in stellar evolution, and other clues. I pay particular attention to the role of feedback that would result from higher mass-loss rates, driving the star to the Eddington limit too soon, and therefore making higher rates appear highly implausible. Some of these arguments by themselves may have more than one interpretation, but together they paint a consistent picture that steady line-driven winds of O-type stars have lower mass-loss rates and are significantly clumped.},
  language  = {en}
}
@inproceedings{FullertonMassaPrinja2007,
  author    = {Fullerton, A. W. and Massa, D. L. and Prinja, R. K.},
  title     = {Revised mass-loss rates for O stars from the Pv resonance line},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17647},
  year      = {2007},
  abstract  = {The P v λλ1118, 1128 resonance doublet is an extraordinarily useful diagnostic of O-star winds, because it bypasses the traditional problems associated with determining mass-loss rates from UV resonance lines. We discuss critically the assumptions and uncertainties involved with using P v to diagnose mass-loss rates, and conclude that the large discrepancies between massloss rates determined from P v and the rates determined from "density squared" emission processes pose a significant challenge to the "standard model" of hot-star winds. The disparate measurements can be reconciled if the winds of O-type stars are strongly clumped on small spatial scales, which in turn implies that mass-loss rates based on Hα or radio emission are too large by up to an order of magnitude.},
  language  = {en}
}
@misc{WackervonElert2002,
  author    = {Wacker, Alexander and von Elert, Eric},
  title     = {Strong influences of larval diet history on subsequent post-settlement growth in the freshwater mollusc Dreissena polymorpha},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17627},
  year      = {2002},
  abstract  = {Significant seasonal variation in size at settlement has been observed in newly settled larvae of Dreissena polymorpha in Lake Constance. Diet quality, which varies temporally and spatially in freshwater habitats, has been suggested as a significant factor influencing life history and development of freshwater invertebrates. Accordingly, experiments were conducted with field-collected larvae to test the hypothesis that diet quality can determine planktonic larval growth rates, size at settlement and subsequent post-metamorphic growth rates. Larvae were fed one of two diets or starved. One diet was composed of cyanobacterial cells which are deficient in polyunsaturated fatty acids (PUFAs), and the other was a mixed diet rich in PUFAs. Freshly metamorphosed animals from the starvation treatment had a carbon content per individual 70\% lower than that of larvae fed the mixed diet. This apparent exhaustion of larval internal reserves resulted in a 50\% reduction of the postmetamorphic growth rates. Growth was also reduced in animals previously fed the cyanobacterial diet. Hence, low food quantity or low food quality during the larval stage of D. polymorpha lead to irreversible effects for postmetamorphic animals, and is related to inferior competitive abilities.},
  language  = {en}
}
@inproceedings{Moffat2007,
  author    = {Moffat, Anthony F. J.},
  title     = {Observational overview of clumping in hot stellar winds},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17633},
  year      = {2007},
  abstract  = {In the old days (pre ∼1990) hot stellar winds were assumed to be smooth, which made life fairly easy and bothered no one. Then after suspicious behaviour had been revealed, e.g. stochastic temporal variability in broadband polarimetry of single hot stars, it took the emerging CCD technology developed in the preceding decades (∼1970-80's) to reveal that these winds were far from smooth. It was mainly high-S/N, time-dependent spectroscopy of strong optical recombination emission lines in WR, and also a few OB and other stars with strong hot winds, that indicated all hot stellar winds likely to be pervaded by thousands of multiscale (compressible supersonic turbulent?) structures, whose driver is probably some kind of radiative instability. Quantitative estimates of clumping-independent mass-loss rates came from various fronts, mainly dependent directly on density (e.g. electron-scattering wings of emission lines, UV spectroscopy of weak resonance lines, and binary-star properties including orbital-period changes, electron-scattering, and X-ray fluxes from colliding winds) rather than the more common, easier-to-obtain but clumping-dependent density-squared diagnostics (e.g. free-free emission in the IR/radio and recombination lines, of which the favourite has always been Hα). Many big questions still remain, such as: What do the clumps really look like? Do clumping properties change as one recedes from the mother star? Is clumping universal? Does the relative clumping correction depend on \$\dot{M}\$ itself?},
  language  = {en}
}
@inproceedings{Hirschi2007,
  author    = {Hirschi, Raphael},
  title     = {The impact of reduced mass loss rates on the evolution of massive stars},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17616},
  year      = {2007},
  abstract  = {Mass loss is a very important aspect of the life of massive stars. After briefly reviewing its importance, we discuss the impact of the recently proposed downward revision of mass loss rates due to clumping (difficulty to form Wolf-Rayet stars and production of critically rotating stars). Although a small reduction might be allowed, large reduction factors around ten are disfavoured. We then discuss the possibility of significant mass loss at very low metallicity due to stars reaching break-up velocities and especially due to the metal enrichment of the surface of the star via rotational and convective mixing. This significant mass loss may help the first very massive stars avoid the fate of pair-creation supernova, the chemical signature of which is not observed in extremely metal poor stars. The chemical composition of the very low metallicity winds is very similar to that of the most metal poor star known to date, HE1327-2326 and offer an interesting explanation for the origin of the metals in this star. We also discuss the importance of mass loss in the context of long and soft gamma-ray bursts and pair-creation supernovae. Finally, we would like to stress that mass loss in cooler parts of the HR-diagram (luminous blue variable and yellow and red supergiant stages) are much more uncertain than in the hot part. More work needs to be done in these areas to better constrain the evolution of the most massive stars.},
  language  = {en}
}
@misc{WackervonElert2001,
  author    = {Wacker, Alexander and von Elert, Eric},
  title     = {Polyunsaturated fatty acids : evidence for non-substitutable biochemical resources in Daphnia galeata},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17587},
  year      = {2001},
  abstract  = {The factors that determine the efficiency of energy transfer in aquatic food webs have been investigated for many decades. The plant-animal interface is the most variable and least predictable of all levels in the food web. In order to study determinants of food quality in a large lake and to test the recently proposed central importance of the long-chained eicosapentaenoic acid (EPA) at the pelagic producer-grazer interface, we tested the importance of polyunsaturated fatty acids (PUFAs) at the pelagic producerconsumer interface by correlating sestonic food parameters with somatic growth rates of a clone of Daphnia galeata. Daphnia growth rates were obtained from standardized laboratory experiments spanning one season with Daphnia feeding on natural seston from Lake Constance, a large pre-alpine lake. Somatic growth rates were fitted to sestonic parameters by using a saturation function. A moderate amount of variation was explained when the model included the elemental parameters carbon (r2 = 0.6) and nitrogen (r2 = 0.71). A tighter fit was obtained when sestonic phosphorus was incorporated (r2 = 0.86). The nonlinear regression with EPA was relatively weak (r2 = 0.77), whereas the highest degree of variance was explained by three C18-PUFAs. The best (r2 = 0.95), and only significant, correlation of Daphnia's growth was found with the C18-PUFA α-linolenic acid (α-LA; C18:3n-3). This correlation was weakest in late August when C:P values increased to 300, suggesting that mineral and PUFA-limitation of Daphnia's growth changed seasonally. Sestonic phosphorus and some PUFAs showed not only tight correlations with growth, but also with sestonic α-LA content. We computed Monte Carlo simulations to test whether the observed effects of α-LA on growth could be accounted for by EPA, phosphorus, or one of the two C18-PUFAs, stearidonic acid (C18:4n-3) and linoleic acid (C18:2n-6). With >99 \% probability, the correlation of growth with α-LA could not be explained by any of these parameters. In order to test for EPA limitation of Daphnia's growth, in parallel with experiments on pure seston, growth was determined on seston supplemented with chemostat-grown, P-limited Stephanodiscus hantzschii, which is rich in EPA. Although supplementation increased the EPA content 80-800x, no significant changes in the nonlinear regression of the growth rates with α-LA were found, indicating that growth of Daphnia on pure seston was not EPA limited. This indicates that the two fatty acids, EPA and α-LA, were not mutually substitutable biochemical resources and points to different physiological functions of these two PUFAs. These results support the PUFA-limitation hypothesis for sestonic C:P < 300 but are contrary to the hypothesis of a general importance of EPA, since no evidence for EPA limitation was found. It is suggested that the resource ratios of EPA and α-LA rather than the absolute concentrations determine which of the two resources is limiting growth.},
  language  = {en}
}
@misc{PeterAndersenHartmannetal.1992,
  author    = {Peter, Martin G. and Andersen, Svend Olav and Hartmann, Rudolf and Miessner, Merle and Roepstorff, Peter},
  title     = {Catecholamine-protein conjugates : isolation of 4-phenylphenoxazin-2-ones from oxidative coupling of N-acetyldopamine with alipathic amino acids},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17571},
  year      = {1992},
  abstract  = {4-Phenylphenoxazinones were isolated after biomimetic oxidation, using diphenoloxidases of insect cuticle, mushroom tyrosinase, or after autoxidation of N-acetyldopamine (Image ) in the presence of β-alanine, β-alanine methyl ester or N-acetyl-L-lysine. They are formed presumably by addition of 2-aminoalkyl-5-alkylphenols to the o-quinone of biphenyltetrol which, in turn, arises from oxidative coupling of. The structures of present the first examples for the assembly of reasonably stable intermediates in the rather complex process of chemical modifications of aliphatic amino acid residues by o-quinones.},
  language  = {en}
}
@misc{Laschewsky1989,
  author    = {Laschewsky, Andr{\´e}},
  title     = {Monolayers and Langmuir-Blodgett multilayers of discotic liquid crystals?},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17396},
  year      = {1989},
  abstract  = {Contents: 1. Discotic Liquid Crystals 2. Monolayers and Langmuir-Blodgett Multilayers 3. Theoretical Considerations on the Molecular Packing of Discotic LCs in Monolayers and Multilayers 4. Spreading Experiments with Discotic LCs 5. LB-Multilayers of Discotic LCs 6. Polymeric Discotic LCs 7. Summary},
  language  = {en}
}
@misc{LaschewskyPaulusRingsdorfetal.1992,
  author    = {Laschewsky, Andr{\´e} and Paulus, Wolfgang and Ringsdorf, Helmut and Schuster, A. and Frick, G. and Mathy, A.},
  title     = {Mixed polymeric monolayers and Langmuir-Blodgett multilayers with functional low molecular weight guest compounds},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17233},
  year      = {1992},
  abstract  = {Mixed monolayers and Langmuir-Blodgett multilayers of functional low molecular weight guest compounds, especially nonlinear optical (NLO) dyes, within the matrix of an amphotropic spacer polymer have been prepared. The polymer matrix enabled the transfer of guest compounds not capable of self-organizing at the air-water interface by themselves. The structure of the LB multilayers and the transfer process were studied by small angle X-ray scattering and UV-visible spectroscopy. Good NLO coefficients were found in the mixed films.},
  language  = {en}
}
@misc{Laschewsky1991,
  author    = {Laschewsky, Andr{\´e}},
  title     = {Oligoethyleneoxide spacer groups in polymerizable surfactants},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17221},
  year      = {1991},
  abstract  = {Cationic and zwitterionic polymerizable surfactants bearing tri- and tetraethyleneglycol spacer groups between the polymerizable moiety and the surfactant structure were prepared and polymerized. Monomers and polymers were investigated with respect to their aggregation behavior in aqueous systems and compared to analogous monomers and polymers lacking spacer groups. In the case of the monomeric surfactants, the spacer groups depress both the Kraffttemperature and the critical micelle concentration. the area occupied per molecule at the air-water interface is substantially enlarged by the spacers, whereas the depression of surface tension is nearly constant. Although the monomers with and without spacers are true surfactants, all the polymers are water-insoluble, but form monomolecular layers at the air-water interface. In analogy to the monomer behavior, the incorporation of the spacer groups increases the area occupied per repeat unit at the air-water interface substantially, but hardly affects the surface activity.},
  language  = {en}
}
@misc{LaschewskyRingsdorf1988,
  author    = {Laschewsky, Andr{\´e} and Ringsdorf, H.},
  title     = {Polymerization of amphiphilic dienes in Langmuir-Blodgett multilayers},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17176},
  year      = {1988},
  abstract  = {Amphiphilic derivatives of octadiene and docosadiene were investigated in monolayers and Langmuir-Blodgett multilayers, with respect to their self-organization and their polymerization behavior. All amphiphiles investigated form monolayers. However, only acid and alcohol derivatives were able to build up multilayers. Those multilayers are rapidly photopolymerized in the layers via a two-step process: Irradiation with long-wavelength UV light yields soluble polymers, whereas additional irradiation with sfiort-wavelength UV light produces insoluble and presumably cross-linked polymers. The reaction meclianism is discussed according to the polymer characterization by UV spectroscopy, small-angle X-ray scattering, NMR spectroscopy, and gel permeation chromatography. All multilayers undergo structural changes during the polymerization; substantial changes result in defects in the polymerized layers as observed by scanning electron microscopy. In contrast to the acids and alcohols, the deposition of monolayers of the aldehyde derivatives did not yield well-ordered multilayers, but rather amorphous films. In this different film structure, the photopolymerization process differs from the one observed in multilayers.},
  language  = {en}
}
@misc{LaschewskyRingsdorfSchmidtetal.1987,
  author    = {Laschewsky, Andr{\´e} and Ringsdorf, H. and Schmidt, G. and Schneider, J.},
  title     = {Self-organization of polymeric lipids with hydrophilic spacers in side groups and main chain : investigation in monolayers and multilayers},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17147},
  year      = {1987},
  abstract  = {Several polymerizable lipids were synthesized and polymerized to amphiphilic homopolymers and to copolymers with the help of hydrophilic comonomers. The self-organization of these polymeric lipids was investigated in monolayers and Langmuir-Blodgett multilayers. The self-organization of these polymers in model membranes is due to hydrophilic spacer groups in the amphiphilic side groups as well as to hydrophilic spacer groups in the polymer backbone. Thus, highly ordered monolayers and LB-multilayers are easily obtained.},
  language  = {en}
}
@misc{LaschewskyRingsdorfSchneider1986,
  author    = {Laschewsky, Andr{\´e} and Ringsdorf, H. and Schneider, J.},
  title     = {Oriented supramolecular systems-polymeric monolayers and multilayers from prepolymerized amphiphiles},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17131},
  year      = {1986},
  abstract  = {Oriented polymeric membranes were originally prepared by polymerization or polycondensation of preoriented monomers. The introduction of hydrophilic spacer groups into the polymeric amphiphiles allowed the formation of highly ordered systems (monolayers, liposomes, multilayers) from prepolymerized amphiphiles: due to the partial decoupling of the different mobilities and orientation tendencies of the polymer chain and the amphiphilic side groups, these polymers are able to self-organize. In monolayer experiments the high order of these membranes could be demonstrated by their surface pressure area-diagrams. In addition the combination of order and mobility of these spacer groups containing polymeric amphiphiles allowed the formation of Langmuir-Blodgett-multilyers with a high layer correlation. Thus, disturbancies in highly oriented layers can be avoided normally taking place during the polymerization reaction (e.g. contractions) or oriented monomeric layers.},
  language  = {en}
}
@misc{LaschewskyRingsdorfSchmidt1985,
  author    = {Laschewsky, Andr{\´e} and Ringsdorf, H. and Schmidt, G.},
  title     = {Polymerization of hydrocarbon and fluorocarbon amphiphiles in Langmuir-Blodgett multilayers},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17096},
  year      = {1985},
  abstract  = {Langmuir-Blodgett multilayers of polymerizable carboxylic acids with hydrocarbon or fluorocarbon chains were prepared. The multilayers were polymerized by UV light and the reactions were studied by UV/visible spectroscopy. The polyreactions strongly influence the multilayer structures which were investigated by X-ray small-angle scattering and scanning electron microscopy. The spreading behaviour of the monomers, the preparation of multilayers, their reactivities in multilayers and structural effects caused by the polyreactions are discussed with regard to the hydrophilic head groups, the polymerizable groups and the hydrophobic chains.},
  language  = {en}
}
@misc{PeterFoerster1989,
  author    = {Peter, Martin G. and F{\"o}rster, Hans},
  title     = {On the structure of Eumelanins : identification of constitutional patterns by solid-state NMR spectroscopy},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17027},
  year      = {1989},
  abstract  = {Aus dem Inhalt: Melanins are complex polyphenolic polymers. They are usually formed in nature by enzyme-catalyzed oxidative polymerization of o-diphenols. The deep black eumelanins, derived from Dopa 1 or dopamine 3, are distinguished from the yellow to brown phaeomelanins obtained from Dopa in the presence of cysteine. Characteristic of eumelanins are the indole units, which are formed from catecholamines by intramolecular addition of the amino groups to the oxidatively generated o-quinones. [...]},
  language  = {en}
}
@misc{ElsenbeerCasselCastro1992,
  author    = {Elsenbeer, Helmut and Cassel, Keith and Castro, Jorge},
  title     = {Spatial analysis of soil hydraulic conductivity in a tropical rain forest catchment},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16979},
  year      = {1992},
  abstract  = {The topography of first-order catchments in a region of western Amazonia was found to exhibit distinctive, recurrent features: a steep, straight lower side slope, a flat or nearly flat terrace at an intermediate elevation between valley floor and interfluve, and an upper side slope connecting interfluve and intermediate terrace. A detailed survey of soil-saturated hydraulic conductivity (K sat)-depth relationships, involving 740 undisturbed soil cores, was conducted in a 0.75-ha first-order catchment. The sampling approach was stratified with respect to the above slope units. Exploratory data analysis suggested fourth-root transformation of batches from the 0-0.1 m depth interval, log transformation of batches from the subsequent 0.1 m depth increments, and the use of robust estimators of location and scale. The K sat of the steep lower side slope decreased from 46 to 0.1 mm/h over the overall sampling depth of 0.4 m. The corresponding decrease was from 46 to 0.1 mm/h on the intermediate terrace, from 335 to 0.01 mm/h on the upper side slope, and from 550 to 0.015 mm/h on the interfluve. A depthwise comparison of these slope units led to the formulation of several hypotheses concerning the link between K sat and topography.},
  language  = {en}
}
@misc{ElsenbeerCasselTinner1993,
  author    = {Elsenbeer, Helmut and Cassel, Keith and Tinner, W.},
  title     = {A daily rainfall erosivity model for Western Amazonia},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16962},
  year      = {1993},
  abstract  = {Rainfall erosivities as defined by the R factor from the universal soil loss equation were determined for all events during a two-year period at the station La Cuenca in western Amazonia. Three methods based on a power relationship between rainfall amount and erosivity were then applied to estimate event and daily rainfall erosivities from the respective rainfall amounts. A test of the resulting regression equations against an independent data set proved all three methods equally adequate in predicting rainfall erosivity from daily rainfall amount. We recommend the Richardson model for testing in the Amazon Basin, and its use with the coefficient from La Cuenca in western Amazonia.},
  language  = {en}
}
@misc{ElsenbeerCasselZuniga1994,
  author    = {Elsenbeer, Helmut and Cassel, Keith and Zu{\~n}iga, L.},
  title     = {Throughfall in the terra firme forest of Western Amazonia},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16955},
  year      = {1994},
  abstract  = {Throughfall measurements were made under primary terra firme rainforest in the Rio Pichis valley, in the Upper Amazon Basin of Peru. Based on 214 precipitation events over nearly 18 months, throughfall was estimated to be 83.1±8.8\% of gross precipitation. Regression analysis of all events revealed that gross precipitation is the only significant explanatory variable; the use of one-burst events does not significantly improve the regression relationship. Gross precipitation is, however, a poor predictor of throughfall for small rainfall events. The two forest structure parameters, canopy capacity, S, and free throughfall coefficient, p, were determined to be 1.3±0.2 mm and 0.32±0.18 mm. Rainfall intensity was found to influence these parameters. New methods which attempt to minimize the influence of meteorologic variables are used to estimate the potential values of these canopy parameters.},
  language  = {en}
}
@misc{ElsenbeerLorieriBonell1995,
  author    = {Elsenbeer, Helmut and Lorieri, Daniel and Bonell, Mike},
  title     = {Mixing model approaches to estimate storm flow sources in an overland flow-dominated tropical rain forest catchment},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16948},
  year      = {1995},
  abstract  = {Previous hydrometric studies demonstrated the prevalence of overland flow as a hydrological pathway in the tropical rain forest catchment of South Creek, northeast Queensland. The purpose of this study was to consider this information in a mixing analysis with the aim of identifying sources of, and of estimating their contribution to, storm flow during two events in February 1993. K and acid-neutralizing capacity (ANC) were used as tracers because they provided the best separation of the potential sources, saturation overland flow, soil water from depths of 0.3, 0.6, and 1.2 m, and hillslope groundwater in a two-dimensional mixing plot. It was necessary to distinguish between saturation overland flow, generated at the soil surface and following unchanneled pathways, and overland flow in incised pathways. This latter type of overland flow was a mixture of saturation overland flow (event water) with high concentrations of K and a low ANC, soil water (preevent water) with low concentrations of K and a low ANC, and groundwater (preevent water) with low concentrations of K and a high ANC. The same sources explained the streamwater chemistry during the two events with strongly differing rainfall and antecedent moisture conditions. The contribution of saturation overland flow dominated the storm flow during the first, high-intensity, 178-mm event, while the contribution of soil water reached 50\% during peak flow of the second, low-intensity, 44-mm event 5 days later. This latter result is remarkably similar to soil water contributions to storm flow in mountainous forested catchments of the southeastern United States. In terms of event and preevent water the storm flow hydrograph of the high-intensity event is dominated by event water and that of the low-intensity event by preevent water. This study highlights the problems of applying mixing analyses to overland flow-dominated catchments and soil environments with a poorly developed vertical chemical zonation and emphasizes the need for independent hydrometric information for a complete characterization of watershed hydrology and chemistry.},
  language  = {en}
}
@misc{ElsenbeerLackCassel1995,
  author    = {Elsenbeer, Helmut and Lack, Andreas and Cassel, Keith},
  title     = {Chemical fingerprints of hydrological compartments and flow paths at La Cuenca, western Amazonia},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16937},
  year      = {1995},
  abstract  = {A forested first-order catchment in western Amazonia was monitored for 2 years to determine the chemical fingerprints of precipitation, throughfall, overland flow, pipe flow, soil water, groundwater, and streamflow. We used five tracers (hydrogen, calcium, magnesium, potassium, and silica) to distinguish "fast" flow paths mainly influenced by the biological subsystem from "slow" flow paths in the geochemical subsystem. The former comprise throughfall, overland flow, and pipe flow and are characterized by a high potassium/silica ratio; the latter are represented by soil water and groundwater, which have a low potassium/silica ratio. Soil water and groundwater differ with respect to calcium and magnesium. The groundwater-controlled streamflow chemistry is strongly modified by contributions from fast flow paths during precipitation events. The high potassium/silica ratio of these flow paths suggests that the storm flow response at La Cuenca is dominated by event water.},
  language  = {en}
}
@misc{ElsenbeerWestBonell1994,
  author    = {Elsenbeer, Helmut and West, Adam and Bonell, Mike},
  title     = {Hydrologic pathways and stormflow hydrochemistry at South Creek, northeast Queensland},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16904},
  year      = {1994},
  abstract  = {Earlier investigations at South Creek in northeastern Queensland established the importance of overland flow as a hydrologic pathway in this tropical rainforest environment. Since this pathway is 'fast', transmitting presumably 'new' water, its importance should be reflected in the stormflow chemistry of South Creek: the greater the volumentric contribution to the stormflow hydrograph, the more similarity between the chemical composition of streamwater and of overland flow is to be expected. Water samples were taken during two storm events in an ephemeral gully (gully A), an intermittent gully (gully B) and at the South Creek catchment outlet; additional spot checks were made in several poorly defined rills. The chemical composition of 'old' water was determined from 45 baseflow samples collected throughout February. The two events differed considerably in their magnitudes, intensities and antecedent moisture conditions. In both events, the stormflow chemistry in South Creek was characterized by a sharp decrease in Ca, Mg, Na, Si, Cl, EC, ANC, alkalinity and total inorganic carbon. pH remained nearly constant with discharge, whereas K increased sharply, as did sulfate in an ill-defined manner. In event 1, this South Creek stormflow pattern was closely matched by the pattern in gully A, implying a dominant contribution of 'new' water. This match was confirmed by the spot samples from rills. Gully B behaved like South Creek itself, but with a dampened 'new' water signal, indicating less overland flow generation in its subcatchment. In event 2, which occurred five days later, the initial 'new' water signal in gully A was rapidly overwhelmed by a different signal which is attributed to rapid drainage from a perched water table. This study shows that stormflow in this rainforest catchment consists predominantly of 'new' water which reaches the stream channel via 'fast' pathways. Where the ephemeral gullies delivering overland flow are incised deeply enough to intersect a perched water table, a delayed, 'old' water-like signal may be transmitted.},
  language  = {en}
}
@misc{KlieglOlsenDavidson1982,
  author    = {Kliegl, Reinhold and Olsen, Richard K. and Davidson, Brian J.},
  title     = {Regression analyses as a tool for studying reading processes : comment on Just and Carpenter's eye fixation theory},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16857},
  year      = {1982},
  abstract  = {Just and Carpenter (1980) presented a theory of reading based on eye fixations wherein their "psycholinguistic" variables accounted for 72\% of the variance in word gaze durations. This comment raises some statistical and theoretical problems with their use of simultaneous regression analysis of gaze duration measures and with the resulting theory of reading. A major problem was the confounding of perceptual with psycholinguistic factors. New eye fixation data are presented to support these criticisms. Analysis of fixations within words revealed that most gaze duration variance was contributed by number of fixations rather than by fixation duration.},
  language  = {en}
}
@misc{Reich1994,
  author    = {Reich, Sebastian},
  title     = {Momentum conserving symplectic integrators},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16824},
  year      = {1994},
  abstract  = {In this paper, we show that symplectic partitioned Runge-Kutta methods conserve momentum maps corresponding to linear symmetry groups acting on the phase space of Hamiltonian differential equations by extended point transformation. We also generalize this result to constrained systems and show how this conservation property relates to the symplectic integration of Lie-Poisson systems on certain submanifolds of the general matrix group GL(n).},
  language  = {en}
}
@misc{Peter1980,
  author    = {Peter, Martin G.},
  title     = {Products of in vitro oxidation of N-acetyldopamine as possible components in the sclerotization of insect cuticle},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16759},
  year      = {1980},
  abstract  = {[1-14C]-N-Acetyldopamine (NADA) was oxidized in the presence of methyl [3-3H]-β-alanate with mushroom tyrosinase. The complex mixture of reaction products was partly resolved by chromatographic procedures and analyzed by spectroscopic methods. Methyl-β-alanate is incorporated to only a small extent into oxidation products of NADA which inter alia are presumed to be oligomeric hydroxyquinones. After oxidation of [1-14C, 2-3H]-NADA with preparations from tanning Manduca sexta pupal cuticle, N-acetylnoradrenalin was identified as one of the products. Binding of radioactivity to melanin-like material was also observed. These results suggest that oxidation products different from those formulated usually for the crosslinkages between protein amino groups and N-acetyldopaquinone are deposited in darkly brown coloured insect cuticles during sclerotization.},
  language  = {en}
}
@misc{PueschelOppermannNeuschaeferRubeetal.1991,
  author    = {P{\"u}schel, Gerhard Paul and Oppermann, Martin and Neusch{\"a}fer-Rube, Frank and G{\"o}tze, Otto and Jungermann, Kurt},
  title     = {Differential effects of human anaphylatoxin C3a on glucose output and flow in rat liver during orthograde and retrograde perfusion : the periportal scavenger cell hypothesis},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16747},
  year      = {1991},
  abstract  = {1) During orthograde perfusion of rat liver human anaphylatoxin C3a caused an increase in glucose and lactate output and reduction of flow. These effects could be enhanced nearly twofold by co-infusion of the carboxypeptidase inhibitor MERGETPA, which reduced inactivation of C3a to C3adesArg. 2) During retrograde perfusion C3a caused a two- to threefold larger increase in glucose and lactate output and reduction of flow than in orthograde perfusions. These actions tended to be slightly enhanced by MERGETPA. 3) The elimination of C3a plus C3adesArg immunoreactivity during a single liver passage was around 67\%, irrespective of the perfusion direction and the presence of the carboxypeptidase inhibitor MERGETPA; however, less C3adesArg and more intact C3a appeared in the perfusate in the presence of MERGETPA in orthograde and retrogade perfusions It is concluded that rat liver inactivated human anaphylatoxin C3a by conversion to C3adesArg and moreover eliminated it by an additional process. The inactivation to C3adesArg seemed to be located predominantly in the proximal periportal region of the liver sinusoid, since C3a was less effective in orthograde perfusions, when C3a first passed the proximal periportal region before reaching the predominant mass of parenchyma as its site of action, than in retrograde perfusions, when it first passed the perivenous area. These data may be evidence for a periportal scavenger mechanism, by which the liver protects itself from systemically released mediators of inflammation that interfere with the local regulation of liver metabolism and hemodynamics.},
  language  = {en}
}
@misc{PueschelOppermannMuscholetal.1989,
  author    = {P{\"u}schel, Gerhard Paul and Oppermann, Martin and Muschol, Waldemar and G{\"o}tze, Otto and Jungermann, Kurt},
  title     = {Increase of glucose and lactate output and decrease of flow by human anaphylatoxin C3a but not C5a in perfused rat liver},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16733},
  year      = {1989},
  abstract  = {The complement fragments C3a and C5a were purified from zymosan-activated human serum by column chromatographic procedures after the bulk of the proteins had been removed by acidic polyethylene glycol precipitation. In the isolated in situ perfused rat liver C3a increased glucose and lactate output and reduced flow. Its effects were enhanced in the presence of the carboxypeptidase inhibitor DL-mercaptomethyl-3-guanidinoethylthio-propanoic acid (MERGETPA) and abolished by preincubation of the anaphylatoxin with carboxypeptidase B or with Fab fragments of an anti-C3a monoclonal antibody. The C3a effects were partially inhibited by the thromboxane antagonist BM13505. C5a had no effect. It is concluded that locally but not systemically produced C3a may play an important role in the regulation of local metabolism and hemodynamics during inflammatory processes in the liver.},
  language  = {en}
}
@misc{PueschelNathJungermann1987,
  author    = {P{\"u}schel, Gerhard Paul and Nath, Annegret and Jungermann, Kurt},
  title     = {Increase of urate formation by stimulation of sympathetic hepatic nerves, circulating noradrenaline and glucagon inthe perfused rat liver},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16728},
  year      = {1987},
  abstract  = {In the isolated rat liver perfused in situ stimulation of the nerve bundles around the portal vein and the hepatic artery caused an increase of urate formation that was inhibited by the α1-blocker prazosine and the xanthine oxidase inhibitor allopurinol. Moreover, nerve stimulation increased glucose and lactate output and decreased perfusion flow. Infusion of noradrenaline had similar effects. Compared to nerve stimulation infusion of glucagon led to a less pronounced increase of urate formation and a twice as large increase in glucose output but a decrease in lactate release without affecting the flow rate. Insulin had no effect on any of the parameters studied.},
  language  = {en}
}
@book{OPUS4-1537,
  title     = {Interdisciplinary studies on information structure : ISIS ; Working papers of the SFB 632. - Vol. 10},
  editor    = {Ishihara, Shinichiro and Schwarz, Anne},
  issn      = {1866-4725},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16929},
  publisher      = {Universit{\"a}t Potsdam},
  year      = {2008},
  abstract  = {The 10th volume of the working paper series contains two papers contributed by SFB-members. The first paper "Single prosodic phrase sentences" by Caroline F{\´e}ry (A1) and Heiner Drenhaus (C6, University of Potsdam) investigates the prosody of Wide Focus Partial Fronting in a series of production and perception experiments. The second paper "Focus Asymmetries in Bura" by Katharina Hartmann, Peggy Jacob (B2, Humboldt University Berlin) and Malte Zimmermann (A5, University of Potsdam) explores the strategies of marking focus in Bura (Chadic).},
  language  = {en}
}
@misc{PueschelHespelingOppermannetal.1993,
  author    = {P{\"u}schel, Gerhard Paul and Hespeling, Ursula and Oppermann, Martin and Dieter, Peter},
  title     = {Increase in prostanoid formation in rat liver macrophages (Kupffer cells) by human anaphylatoxin C3a},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16716},
  year      = {1993},
  abstract  = {Human anaphylatoxin C3a increases glycogenolysis in perfused rat liver. This action is inhibited by prostanoid synthesis inhibitors and prostanoid antagonists. Because prostanoids but not anaphylatoxin C3a can increase glycogenolysis in hepatocytes, it has been proposed that prostanoid formation in nonparenchymal cells represents an important step in the C3a-dependent increase in hepatic glycogenolysis. This study shows that (a) human anaphylatoxin C3a (0.1 to 10 mug/ml) dose-dependently increased prostaglandin D2, thromboxane B, and prostaglandin F2alpha formation in rat liver macrophages (Kupffer cells); (b) the C3a-mediated increase in prostanoid formation was maximal after 2 min and showed tachyphylaxis; and (c) the C3a-elicited prostanoid formation could be inhibited specifically by preincubation of C3a with carboxypeptidase B to remove the essential C-terminal arginine or by preincubation of C3a with Fab fragments of a neutralizing monoclonal antibody. These data support the hypothesis that the C3a-dependent activation of hepatic glycogenolysis is mediated by way of a C3a-induced prostanoid production in Kupffer cells.},
  language  = {en}
}
@misc{HespelingJungermannPueschel1995,
  author    = {Hespeling, Ursula and Jungermann, Kurt and P{\"u}schel, Gerhard Paul},
  title     = {Feedback-inhibition of glucagon-stimulated glycogenolysis in hepatocyte/kupffer cell cocultures by glucagon-elicited prostaglandin production in kupffer cells},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16697},
  year      = {1995},
  abstract  = {Prostaglandins, released from Kupffer cells, have been shown to mediate the increase in hepatic glycogenolysis by various stimuli such as zymosan, endotoxin, immune complexes, and anaphylotoxin C3a involving prostaglandin (PG) receptors coupled to phospholipase C via a G(0) protein. PGs also decreased glucagon-stimulated glycogenolysis in hepatocytes by a different signal chain involving PGE(2) receptors coupled to adenylate cyclase via a G(i) protein (EP(3) receptors). The source of the prostaglandins for this latter glucagon-antagonistic action is so far unknown. This study provides evidence that Kupffer cells may be one source: in Kupffer cells, maintained in primary culture for 72 hours, glucagon (0.1 to 10 nmol/ L) increased PGE(2), PGF(2 alpha), and PGD(2) synthesis rapidly and transiently. Maximal prostaglandin concentrations were reached after 5 minutes. Glucagon (1 nmol/L) elevated the cyclic adenosine monophosphate (cAMP) and inositol triphosphate (InsP(3)) levels in Kupffer cells about fivefold and twofold, respectively. The increase in glyco gen phosphorylase activity elicited by 1 nmol/L glucagon was about twice as large in monocultures of hepatocytes than in cocultures of hepatocytes and Kupffer cells with the same hepatocyte density. Treatment of cocultures with 500 mu mol/L acetylsalicylic acid (ASA) to irreversibly inhibit cyclooxygenase (PGH-synthase) 30 minutes before addition of glucagon abolished this difference. These data support the hypothesis that PGs produced by Kupffer cells in response to glucagon might participate in a feedback loop inhibiting glucagon-stimulated glycogenolysis in hepatocytes.},
  language  = {en}
}
@misc{KoechyBrakenhielm2008,
  author    = {K{\"o}chy, Martin and Br{\aa}kenhielm, Sven},
  title     = {Separation of effects of moderate N deposition from natural change in ground vegetation of forests and bogs},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16621},
  year      = {2008},
  abstract  = {The effect of moderate rates of nitrogen deposition on ground floor vegetation is poorly predicted by uncontrolled surveys or fertilization experiments using high rates of nitrogen (N) addition. We compared the temporal trends of ground floor vegetation in permanent plots with moderate (7-13 kg ha-1 year-1) and lower bulk N deposition (4-6 kg ha-1 year-1) in southern Sweden during 1982-1998. We examined whether trends differed between growth forms (vascular plants and bryophytes) and vegetation types (three types of coniferous forest, deciduous forest, and bog). Trends of site-standardized cover and richness varied among growth forms, vegetation types, and deposition regions. Cover in spruce forests decreased at the same rate with both moderate and low deposition. In pine forests cover decreased faster with moderate deposition and in bogs cover decreased faster with low deposition. Cover of bryophytes in spruce forests increased at the same rate with both moderate and low deposition. In pine forests cover decreased faster with moderate deposition and in bogs and deciduous forests there was a strong non-linear increase with moderate deposition. The trend of number of vascular plants was constant with moderate and decreased with low deposition. We found no trend in the number of bryophyte species. We propose that the decrease of cover and number with low deposition was related to normal ecosystem development (increased shading), suggesting that N deposition maintained or increased the competitiveness of some species in the moderate-deposition region. Deposition had no consistent negative effect on vegetation suggesting that it is less important than normal successional processes.},
  language  = {en}
}
@phdthesis{Wasiolka2007,
  author    = {Wasiolka, Bernd},
  title     = {The impact of overgrazing on reptile diversity and population dynamics of Pedioplanis l. lineoocellata in the southern Kalahari},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16611},
  school      = {Universit{\"a}t Potsdam},
  year      = {2007},
  abstract  = {Die Vegetationskomposition und -struktur, beispielsweise die unterschiedliche Architektur von B{\"a}umen, Str{\"a}uchern, Gr{\"a}sern und Kr{\"a}utern, bietet ein großes Spektrum an Habitaten und Nischen, die wiederum eine hohe Tierdiversit{\"a}t in den Savannensystemen des s{\"u}dlichen Afrikas erm{\"o}glichen. Dieses {\"O}kosystem wurde jedoch {\"u}ber Jahrzehnte weltweit durch intensive anthropogene Landnutzung (z.B. Viehwirtschaft) nachhaltig ver{\"a}ndert. Dabei wurden die Zusammensetzung, Diversit{\"a}t und Struktur der Vegetation stark ver{\"a}ndert. {\"U}berweidung in Savannensystemen f{\"u}hrt zu einer Degradation des Habitates einhergehend mit dem Verlust von perennierenden Gr{\"a}sern und krautiger Vegetation. Dies f{\"u}hrt zu einem Anstieg an vegetationsfreien Bodenfl{\"a}chen. Beides, sowohl der Verlust an perennierenden Gr{\"a}sern und krautiger Vegetation sowie der Anstieg an vegetationsfreien Fl{\"a}chen f{\"u}hrt zu verbesserten Etablierungsbedingungen f{\"u}r Str{\"a}ucher (z.B. Rhigozum trichotomum, Acacia mellifera) und auf lange Sicht zu stark verbuschten Fl{\"a}chen. Die Tierdiversit{\"a}t in Savannen ist hiervon entscheidend beeinflusst. Mit sinkender struktureller Diversit{\"a}t verringert sich auch die Tierdiversit{\"a}t. W{\"a}hrend der Einfluss von {\"U}berweidung auf die Vegetation relativ gut untersucht ist sind Informationen {\"u}ber den Einfluss von {\"U}berweidung auf die Tierdiversit{\"a}t, speziell f{\"u}r Reptilien, eher sp{\"a}rlich vorhanden. Zus{\"a}tzlich ist sehr wenig bekannt zum Einfluss auf die Populationsdynamik (z.B. Verhaltensanpassungen, Raumnutzung, {\"U}berlebensrate, Sterberate) einzelner Reptilienarten. Ziel meiner Doktorarbeit ist es den Einfluss von {\"U}berweidung durch kommerzielle Farmnutzung auf die Reptiliengemeinschaft und auf verschiedene Aspekte der Populationsdynamik der Echse Pedioplanis lineoocellata lineoocellata zu untersuchen. Hinsichtlich bestimmter Naturschutzmaßnahmen ist es einerseits wichtig zu verstehen welchen Auswirkungen {\"U}berweidung auf die gesamte Reptiliengemeinschaft hat. Und zum anderen wie entscheidende Faktoren der Populationsdynamik beeinflusst werden. Beides f{\"u}hrt zu einem besseren Verst{\"a}ndnis der Reaktion von Reptilien auf Habitatdegradation zu erlangen. Die Ergebnisse meiner Doktorarbeit zeigen eindeutig einen negativen Einfluss der {\"U}berweidung und der daraus resultierende Habitatdegradation auf (1) die gesamte Reptiliengemeinschaft und (2) auf einzelne Aspekte der Populationsdynamik von P. lineoocellata. Im Teil 1 wird die signifikante Reduzierung der Reptiliendiversit{\"a}t und Abundanz in degradierten Habitaten beschrieben. Im zweiten Teil wird gezeigt, dass P. lineoocellata das Verhalten an die verschlechterten Lebensbedingungen anpassen kann. Die Art bewegt sich sowohl h{\"a}ufiger als auch {\"u}ber einen l{\"a}ngeren Zeitraum und legt dabei gr{\"o}ßere Distanzen zur{\"u}ck. Zus{\"a}tzlich vergr{\"o}ßerte die Art ihr Revier (home range) (Teil 3). Im abschließenden Teil wird der negative Einfluss von {\"U}berweidung auf die Populationsdynamik von P. lineoocellata beschrieben: In degradierten Habitaten nimmt die Populationsgr{\"o}ße von adulten und juvenilen Echsen ab, die {\"U}berlebens- und Geburtenrate sinken, w{\"a}hren zus{\"a}tzlich das Pr{\"a}dationsrisiko ansteigt. Verantwortlich hierf{\"u}r ist zum einen die ebenfalls reduzierte Nahrungsverf{\"u}gbarkeit (Arthropoden) auf degradierten Fl{\"a}chen. Dies hat zur Folge, dass die Populationsgr{\"o}ße abnimmt und die Fitness der Individuen verringert wird, welches sich durch eine Reduzierung der {\"U}berlebens- und Geburtenrate bemerkbar macht. Und zum anderen ist es die Reduzierung der Vegetationsbedeckung und der R{\"u}ckgang an perennierenden Gr{\"a}sern welche sich negativ auswirken. Als Konsequenz hiervon gehen Nischen und Mikrohabitate verloren und die M{\"o}glichkeiten der Reptilien zur Thermoregulation sind verringert. Des Weiteren hat dieser Verlust an perennierender Grasbedeckung auch ein erh{\"o}htes Pr{\"a}dationsrisikos zur Folge. Zusammenfassend l{\"a}sst sich sagen, dass nicht nur B{\"a}ume und Str{\"a}ucher, wie in anderen Studien gezeigt, eine bedeutende Rolle f{\"u}r die Diversit{\"a}t spielen, sondern auch das perennierende Gras eine wichtige Rolle f{\"u}r die Faunendiversit{\"a}t spielt. Weiterhin zeigte sich, dass Habitatdegradation nicht nur die Population als gesamtes beeinflusst, sondern auch das Verhalten und Populationsparameter einzelner Arten. Des Weiteren ist es Reptilien m{\"o}glich durch Verhaltensflexibilit{\"a}t auf verschlechterte Umweltbedingen zu reagieren.},
  language  = {en}
}
@misc{OttvandeVijverHoehle2006,
  author    = {Ott, Susan and van de Vijver, Ruben and H{\"o}hle, Barbara},
  title     = {The effect of phonotactic constraints in German-speaking children with delayed phonological acquisition : evidence from production of word-initial consonant clusters},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16316},
  year      = {2006},
  abstract  = {In this study the effect of phonotactic constraints concerning word-initial consonant clusters in children with delayed phonological acquisition was explored. Twelve German-speaking children took part (mean age 5;1). The spontaneous speech of all children was characterized by the regular appearance of the error patterns fronting, e.g., Kuh (cow) → /tu:/, or stopping, e.g., Schaf (sheep) → /ta:f/, which were inappropriate for their chronological age. The children were asked to produce words (picture naming task, word repetition task) with initial consonant clusters, in which the application of the error patterns would violate phonotactic sequence constraints. For instance, if fronting would apply in /kl-/, e.g., Kleid (dress), it would be realized as the phontactically illegal consonant cluster /tl-/. The results indicate that phonotactic constraints affect word production in children with delayed phonological developments. Surprisingly, we found that children with fronting produced the critical consonants correctly significantly more often in word-initial consonant clusters than in words in which they appeared as singleton onsets. In addition, the results provide evidence for a similar developmental trajectory of acquisition in children with typical development and in children with delayed phonological acquisition. Keywords: Children with delayed phonological acquisition, phonotactic constraints, word-initial consonant clusters, fronting, stopping.},
  language  = {en}
}
@misc{HoehlevandeVijverWeissenborn2006,
  author    = {H{\"o}hle, Barbara and van de Vijver, Ruben and Weissenborn, J{\"u}rgen},
  title     = {Word processing at 19 months and its relation to language performance at 30 months : a retrospective analysis of data from German learning children},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16302},
  year      = {2006},
  abstract  = {Recent research has shown that the early lexical representations children establish in their second year of life already seem to be phonologically detailed enough to allow differentiation from very similar forms. In contrast to these findings children with specific language impairment show problems in discriminating phonologically similar word forms up to school age. In our study we investigated the question whether there would be differences in the processing of phonological details in normally developing and in children with low language performance in the second year of life. This was done by a retrospective study in which in the processing of phonological details was tested by a preferential looking experiment when the children were 19 months old. At the age of 30 months children were tested with a standardized German test of language comprehension and production (SETK2). The preferential looking data at 19 months revealed an opposite reaction pattern for the two groups: while the children scoring normally in the SETK2 increase their fixations of a pictured object only when it was named with the correct word, children with later low language performance did so only when presented with a phonologically slightly deviant mispronunciation. We suggest that this pattern does not point to a specific deficit in processing phonological information in these children but might be related to an instability of early phonological representations, and/or a generalized problem of information processing as compared to typically developing children.},
  language  = {en}
}
@misc{HoehleSchmitzMuelleretal.2006,
  author    = {H{\"o}hle, Barbara and Schmitz, Michaela and M{\"u}ller, Anja and Weissenborn, J{\"u}rgen},
  title     = {The recognition of discontinuous verbal dependencies by German 19-month-olds : evidence for lexical and structural influences on children's early processing capacities},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16297},
  year      = {2006},
  abstract  = {Recent work has shown that English-learning 18-month-olds can detect the relationship between discontinuous morphemes such as is and -ing in Grandma is always running (Gomez, 2002; Santelmann \& Jusczyk, 1998) but only at a maximum of 3 intervening syllables. In this article we examine the tracking of discontinuous dependencies in children acquiring German. Due to freer word order, German allows for greater distances between dependent elements and a greater syntactic variety of the intervening elements than English does. The aim of this study was to investigate whether factors other than distance may influence the child's capacity to recognize discontinuous elements. Our findings provide evidence that children's recognition capacities are affected not only by distance but also by their ability to linguistically analyze the material intervening between the dependent elements. We speculate that this result supports the existence of processing mechanisms that reduce a discontinuous relation to a local one based on subcategorization relations.},
  language  = {en}
}
@misc{HoehleWeissenbornKieferetal.2004,
  author    = {H{\"o}hle, Barbara and Weissenborn, J{\"u}rgen and Kiefer, Dorothea and Schulz, Antje and Schmitz, Michaela},
  title     = {Functional elements in infants' speech processing : the role of determiners in the syntactic categorization of lexical elements},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-16285},
  year      = {2004},
  abstract  = {How do children determine the syntactic category of novel words? In this article we present the results of 2 experiments that investigated whether German children between 12 and 16 months of age can use distributional knowledge that determiners precede nouns and subject pronouns precede verbs to syntactically categorize adjacent novel words. Evidence from the head-turn preference paradigm shows that, although 12- to 13-month-olds cannot do this, 14- to 16-month-olds are able to use a determiner to categorize a following novel word as a noun. In contrast, no categorization effect was found for a novel word following a subject pronoun. To understand this difference we analyzed adult child-directed speech. This analysis showed that there are in fact stronger co-occurrence relations between determiners and nouns than between subject pronouns and verbs. Thus, in German determiners may be more reliable cues to the syntactic category of an adjacent novel word than are subject pronouns. We propose that the capacity to syntactically categorize novel words, demonstrated here for the first time in children this young, mediates between the recognition of the specific morphosyntactic frame in which a novel word appears and the word-to-world mapping that is needed to build up a semantic representation for the novel word.},
  language  = {en}
}
@misc{AscherChinPetzoldetal.1994,
  author    = {Ascher, Uri M. and Chin, Hongsheng and Petzold, Linda R. and Reich, Sebastian},
  title     = {Stabilization of constrained mechanical systems with DAEs and invariant manifolds},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-15698},
  year      = {1994},
  abstract  = {Many methods have been proposed for the simulation of constrained mechanical systems. The most obvious of these have mild instabilities and drift problems. Consequently, stabilization techniques have been proposed A popular stabilization method is Baumgarte's technique, but the choice of parameters to make it robust has been unclear in practice. Some of the simulation methods that have been proposed and used in computations are reviewed here, from a stability point of view. This involves concepts of differential-algebraic equation (DAE) and ordinary differential equation (ODE) invariants. An explanation of the difficulties that may be encountered using Baumgarte's method is given, and a discussion of why a further quest for better parameter values for this method will always remain frustrating is presented. It is then shown how Baumgarte's method can be improved. An efficient stabilization technique is proposed, which may employ explicit ODE solvers in case of nonstiff or highly oscillatory problems and which relates to coordinate projection methods. Examples of a two-link planar robotic arm and a squeezing mechanism illustrate the effectiveness of this new stabilization method.},
  language  = {en}
}
@misc{LeimkuhlerReich1994,
  author    = {Leimkuhler, Benedict and Reich, Sebastian},
  title     = {Symplectic integration of constrained Hamiltonian systems},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-15653},
  year      = {1994},
  abstract  = {A Hamiltonian system in potential form (formula in the original abstract) subject to smooth constraints on q can be viewed as a Hamiltonian system on a manifold, but numerical computations must be performed in Rn. In this paper methods which reduce "Hamiltonian differential algebraic equations" to ODEs in Euclidean space are examined. The authors study the construction of canonical parameterizations or local charts as well as methods based on the construction of ODE systems in the space in which the constraint manifold is embedded which preserve the constraint manifold as an invariant manifold. In each case, a Hamiltonian system of ordinary differential equations is produced. The stability of the constraint invariants and the behavior of the original Hamiltonian along solutions are investigated both numerically and analytically.},
  language  = {en}
}
@misc{Reich1995,
  author    = {Reich, Sebastian},
  title     = {Smoothed dynamics of highly oscillatory Hamiltonian systems},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-15639},
  year      = {1995},
  abstract  = {We consider the numerical treatment of Hamiltonian systems that contain a potential which grows large when the system deviates from the equilibrium value of the potential. Such systems arise, e.g., in molecular dynamics simulations and the spatial discretization of Hamiltonian partial differential equations. Since the presence of highly oscillatory terms in the solutions forces any explicit integrator to use very small step size, the numerical integration of such systems provides a challenging task. It has been suggested before to replace the strong potential by a holonomic constraint that forces the solutions to stay at the equilibrium value of the potential. This approach has, e.g., been successfully applied to the bond stretching in molecular dynamics simulations. In other cases, such as the bond-angle bending, this methods fails due to the introduced rigidity. Here we give a careful analysis of the analytical problem by means of a smoothing operator. This will lead us to the notion of the smoothed dynamics of a highly oscillatory Hamiltonian system. Based on our analysis, we suggest a new constrained formulation that maintains the flexibility of the system while at the same time suppressing the high-frequency components in the solutions and thus allowing for larger time steps. The new constrained formulation is Hamiltonian and can be discretized by the well-known SHAKE method.},
  language  = {en}
}
@misc{AscherChinReich1994,
  author    = {Ascher, Uri M. and Chin, Hongsheng and Reich, Sebastian},
  title     = {Stabilization of DAEs and invariant manifolds},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-15625},
  year      = {1994},
  abstract  = {Many methods have been proposed for the stabilization of higher index differential-algebraic equations (DAEs). Such methods often involve constraint differentiation and problem stabilization, thus obtaining a stabilized index reduction. A popular method is Baumgarte stabilization, but the choice of parameters to make it robust is unclear in practice. Here we explain why the Baumgarte method may run into trouble. We then show how to improve it. We further develop a unifying theory for stabilization methods which includes many of the various techniques proposed in the literature. Our approach is to (i) consider stabilization of ODEs with invariants, (ii) discretize the stabilizing term in a simple way, generally different from the ODE discretization, and (iii) use orthogonal projections whenever possible. The best methods thus obtained are related to methods of coordinate projection. We discuss them and make concrete algorithmic suggestions.},
  language  = {en}
}
@misc{Riemer2007,
  author    = {Riemer, Nathanael},
  title     = {Stories of the Ma'aseh Book (Maysebook) in the Scriptures of Christian Hebraists},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-15498},
  year      = {2007},
  abstract  = {This document contains a list of the Stories of the Ma'aseh Book (Maysebook) in the Scriptures of Christian Hebraists and exhibits an overview about the reception of the Yiddish literature in the world of letters.},
  language  = {en}
}
@phdthesis{Frankovitch2007,
  author    = {Frankovitch, Christine Marie},
  title     = {Optical methods for monitoring biological parameters of phototropic microorganisms during cultivation},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-15403},
  school      = {Universit{\"a}t Potsdam},
  year      = {2007},
  abstract  = {Phototropic microalgae have a large potential for producing valuable substances for the feed, food, cosmetics, pigment, bioremediation, and pharmacy industries as well as for biotechnological processes. Today it is estimated that the microalgal aquaculture worldwide production is 5000 tons of dry matter per year (not taking into account processed products) making it an approximately \$1.25 billion U.S. per year industry. In this work, several spectroscopic techniques were utilized for the investigation of microalgae cells. Specifically, photondensity wave spectroscopy was applied as a technique for the on-line observation of the culture. For effective evaluation of the photosynthetic growth processes, fast and non-invasive sensor systems that analyze the relevant biological and technical process parameters are preferred. Traditionally, the biomass in a photobioreactor is quantified with the help of turbidimetry measurements, which require extensive calibration. Another problem frequently encountered when using spectral analysis for investigating solutions is that samples of interest are often undiluted and highly scattering and do not adhere to Beer-Lambert's law. Due to the fluorescence properties of chlorophyll, fluorescence spectroscopy techniques including fluorescence lifetime imaging and single photon counting could be applied to provide images of the cells as well as determine the effects of excitation intensity on the fluorescence lifetime, which is an indicator of the condition of the cell. A photon density wave is a sinusoidally intensity-modulated optical wave stemming from a point-source of light, which propagates through diffuse medium and exhibits amplitude and phase variations. Light propagation though strongly scattering media can be described by the P1 approximation to the Boltzmann transport equation. Photon density wave spectroscopy enables the ability to differentiate between scattered and absorbed light, which is desired so that an independent determination of the reduced scattering and absorption coefficients can be made. The absorption coefficient is related to the pigment content in the cells, and the reduced scattering coefficient can be used to characterize physical and morphological properties of the medium and was here applied for the determination of the average cell size.},
  language  = {en}
}
@article{Arnold2007,
  author    = {Arnold, Holger},
  title     = {A linearized DPLL calculus with learning},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-15421},
  year      = {2007},
  abstract  = {This paper describes the proof calculus LD for clausal propositional logic, which is a linearized form of the well-known DPLL calculus extended by clause learning. It is motivated by the demand to model how current SAT solvers built on clause learning are working, while abstracting from decision heuristics and implementation details. The calculus is proved sound and terminating. Further, it is shown that both the original DPLL calculus and the conflict-directed backtracking calculus with clause learning, as it is implemented in many current SAT solvers, are complete and proof-confluent instances of the LD calculus.},
  language  = {en}
}
@inproceedings{OPUS4-1412,
  title     = {The 3rd international IEEE scientific conference on physics and control (PhysCon 2007) : September 3rd-7th 2007 at the University of Potsdam},
  editor    = {Kurths, J{\"u}rgen and Fradkov, Alexander and Chen, Guanrong},
  publisher = {Universit{\"a}tsverlag Potsdam},
  address   = {Potsdam},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-15228},
  pages     = {345},
  year      = {2007},
  abstract  = {During the last few years there was a tremendous growth of scientific activities in the fields related to both Physics and Control theory: nonlinear dynamics, micro- and nanotechnologies, self-organization and complexity, etc. New horizons were opened and new exciting applications emerged. Experts with different backgrounds starting to work together need more opportunities for information exchange to improve mutual understanding and cooperation. The Conference "Physics and Control 2007" is the third international conference focusing on the borderland between Physics and Control with emphasis on both theory and applications. With its 2007 address at Potsdam, Germany, the conference is located for the first time outside of Russia. The major goal of the Conference is to bring together researchers from different scientific communities and to gain some general and unified perspectives in the studies of controlled systems in physics, engineering, chemistry, biology and other natural sciences. We hope that the Conference helps experts in control theory to get acquainted with new interesting problems, and helps experts in physics and related fields to know more about ideas and tools from the modern control theory.},
  language  = {en}
}
@unpublished{VolosevichMeister1998,
  author    = {Volosevich, Alexandra V. and Meister, Claudia-Veronika},
  title     = {Nonlinear interaction of Farley-Buneman waves},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14851},
  year      = {1998},
  abstract  = {The nonlinear interaction of waves excited by the modified two-stream instability (Farley-Buneman instability) is considered. It is found that, during the linear stage of wave growth, the enhanced pressure of the high-frequency part of the waves locally generates a ponderomotive force. This force acts on the plasma particles and redistributes them. Thus an additional electrostatic polarization field occurs, which influences the low-frequency part of the waves. Then, the low-frequency waves also cause a redistribution of the high-frequency waves. In the paper, a self-consistent system of equations is obtained, which describes the nonlinear interaction of the waves. It is shown that the considered mechanism of wave interaction causes a nonlinear stabilization of the high-frequency waves' growth and a formation of local density structures of the charged particles. The density modifications of the charged particles during the non-linear stage of wave growth and the possible interval of aspect angles of the high-frequency waves are estimated.},
  language  = {en}
}
@unpublished{BoeckmannSarkoezi1999,
  author    = {B{\"o}ckmann, Christine and Sark{\"o}zi, Janos},
  title     = {The ill-posed inversion of multiwavelength lidar data by a hybrid method of variable projection},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14847},
  year      = {1999},
  abstract  = {The ill-posed problem of aerosol distribution determination from a small number of backscatter and extinction lidar measurements was solved successfully via a hybrid method by a variable dimension of projection with B-Splines. Numerical simulation results with noisy data at different measurement situations show that it is possible to derive a reconstruction of the aerosol distribution only with 4 measurements.},
  language  = {en}
}
@unpublished{LiperovskyPochotelovLiperovskayaetal.1998,
  author    = {Liperovsky, V.A. and Pochotelov, O.A. and Liperovskaya, E.V. and Parrot, M. and Meister, C.-V. and Alimov, O. A.},
  title     = {Modifications of sporadic E-layers caused by seismic activity},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14799},
  year      = {1998},
  abstract  = {Contents: 1 Introduction 2 Formation and destruction of sporadic E-layers 3 Temporal variations of parameters of sporadic E-layers during earthquake preparation 3.1 Temporal variations of fbEs with time-scales of a few hours 3.2 Study of fbEs variations with characteristic time-scales of 0.5-3 hours 3.3 Variations of the parameters of sporadic E-layers with characteristic time-scales of 15-45 minutes 3.4 Sporadic E-layer variations with characteristic time-scales of 2-15 minutes 4 On the spatial scales of sporadic E-layer disturbances related to seismic activity 5 Complex experimental researches of the ionosphere, electromagnetic noise and the geomagnetic field 5.1 Ionospheric and electromagnetic phenomena of the Kayraccum earthquake in 1985 5.2 Comparison of anomalies with characteristic time-scales of 2-3 hours for ionospheric E- and F-layers, and temporal behaviour of electromagnetic noise emission intensity 5.3 Night airglow emissions in the E-region before earthquakes and sporadic E-layer variations 6 Physical models of lithosphere-ionosphere links 6.1 Lithosphere-ionosphere links due to AGW 6.2 Electromagnetic models for the lithosphere-ionosphere coupling 6.3 Sporadic E-layers as current generators 7 Discussion and conclusion},
  language  = {en}
}
@unpublished{Dicken1998,
  author    = {Dicken, Volker},
  title     = {Simultaneous activity and attenuation reconstruction in emission tomography},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14747},
  year      = {1998},
  abstract  = {In single photon emission computed tomography (SPECT) one is interested in reconstructing the activity distribution f of some radiopharmaceutical. The data gathered suffer from attenuation due to the tissue density µ. Each imaged slice incorporates noisy sample values of the nonlinear attenuated Radon transform (formular at this place in the original abstract) Traditional theory for SPECT reconstruction treats µ as a known parameter. In practical applications, however, µ is not known, but either crudely estimated, determined in costly additional measurements or plainly neglected. We demonstrate that an approximation of both f and µ from SPECT data alone is feasible, leading to quantitatively more accurate SPECT images. The result is based on nonlinear Tikhonov regularization techniques for parameter estimation problems in differential equations combined with Gauss-Newton-CG minimization.},
  language  = {en}
}
@unpublished{MaassPereverzevRamlauetal.1998,
  author    = {Maaß, Peter and Pereverzev, Sergei V. and Ramlau, Ronny and Solodky, Sergei G.},
  title     = {An adaptive discretization for Tikhonov-Phillips regularization with a posteriori parameter selection},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14739},
  year      = {1998},
  abstract  = {The aim of this paper is to describe an efficient strategy for descritizing ill-posed linear operator equations of the first kind: we consider Tikhonov-Phillips-regularization χ^δ α = (a * a + α I)^-1 A * y ^δ with a finite dimensional approximation A n instead of A. We propose a sparse matrix structure which still leads to optimal convergences rates but requires substantially less scalar products for computing A n compared with standard methods.},
  language  = {en}
}
@unpublished{BoeckmannNiebsch1998,
  author    = {B{\"o}ckmann, Christine and Niebsch, Jenny},
  title     = {Examination of the nonlinear LIDAR-operator : the influence of inhomogeneous absorbing spheres on the operator},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14725},
  year      = {1998},
  abstract  = {The determination of the atmospheric aerosol size distribution is an inverse illposed problem. The shape and the material composition of the air-carried particles are two substantial model parameters. Present evaluation algorithms only used an approximation with spherical homogeneous particles. In this paper we propose a new numerically efficient recursive algorithm for inhomogeneous multilayered coated and absorbing particles. Numerical results of real existing particles show that the influence of the two parameters on the model is very important and therefore cannot be ignored.},
  language  = {en}
}
@unpublished{BraunFeudelGuzdar1998,
  author    = {Braun, Robert and Feudel, Fred and Guzdar, Parvez},
  title     = {The route to chaos for a two-dimensional externally driven flow},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14717},
  year      = {1998},
  abstract  = {We have numerically studied the bifurcations and transition to chaos in a two-dimensional fluid for varying values of the Reynolds number. These investigations have been motivated by experiments in fluids, where an array of vortices was driven by an electromotive force. In these experiments, successive changes leading to a complex motion of the vortices, due to increased forcing, have been explored [Tabeling, Perrin, and Fauve, J. Fluid Mech. 213, 511 (1990)]. We model this experiment by means of two-dimensional Navier-Stokes equations with a special external forcing, driving a linear chain of eight counter-rotating vortices, imposing stress-free boundary conditions in the vertical direction and periodic boundary conditions in the horizontal direction. As the strength of the forcing or the Reynolds number is raised, the original stationary vortex array becomes unstable and a complex sequence of bifurcations is observed. Several steady states and periodic branches and a period doubling cascade appear on the route to chaos. For increasing values of the Reynolds number, shear flow develops, for which the spatial scale is large compared to the scale of the forcing. Furthermore, we have investigated the influence of the aspect ratio of the container as well as the effect of no-slip boundary conditions at the top and bottom, on the bifurcation scenario.},
  language  = {en}
}
@unpublished{Lukaschewitsch1998,
  author    = {Lukaschewitsch, Michael},
  title     = {Geoelectrical conductivity problems on unbounded domains},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14704},
  year      = {1998},
  abstract  = {This paper deals with the electrical conductivity problem in geophysics. It is formulated as an elliptic boundary value problem of second order for a large class of bounded and unbounded domains. A special boundary condition, the so called "Complete Electrode Model", is used. Poincar{\´e} inequalities are formulated and proved in the context of weighted Sobolev spaces, leading to existence and uniqueness statements for the boundary value problem. In addition, a parameter-to-solution operator arising from the inverse conductivity problem in medicine (EIT) and geophysics is investigated mathematically and is shown to be smooth and analytic.},
  language  = {en}
}
@misc{Koechy2006,
  author    = {K{\"o}chy, Martin},
  title     = {Opposite trends in life stages of annual plants caused by daily rainfall variability},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14699},
  pages     = {347 -- 357},
  year      = {2006},
  abstract  = {Global Circulation Models of climate predict not only a change of annual precipitation amounts but also a shift in the daily distribution. To improve the understanding of the importance of daily rain pattern for annual plant communities, which represent a large portion of semi-natural vegetation in the Middle East, I used a detailed, spatially explicit model. The model explicitly considers water storage in the soil and has been parameterized and validated with data collected in field experiments in Israel and data from the literature. I manipulated daily rainfall variability by increasing the mean daily rain intensity on rainy days (MDI, rain volume/day) and decreasing intervals between rainy days while keeping the mean annual amount constant. In factorial combination, I also increased mean annual precipitation (MAP). I considered five climatic regions characterized by 100, 300, 450, 600, and 800 mm MAP. Increasing MDI decreased establishment when MAP was >250 mm but increased establishment at more arid sites. The negative effect of increasing MDI was compensated by increasing mortality with increasing MDI in dry and typical Mediterranean regions (c. 360-720 mm MAP). These effects were strongly tied to water availability in upper and lower soil layers and modified by competition among seedlings and adults. Increasing MAP generally increased water availability, establishment, and density. The order of magnitudes of MDI and MAP effects overlapped partially so that their combined effect is important for projections of climate change effects on annual vegetation. The effect size of MAP and MDI followed a sigmoid curve along the MAP gradient indicating that the semi-arid region (≈300 mm MAP) is the most sensitive to precipitation change with regard to annual communitie},
  subject      = {Klima{\"a}nderung},
  language  = {en}
}
@unpublished{SeehaferSchumacher1998,
  author    = {Seehafer, Norbert and Schumacher, J{\"o}rg},
  title     = {Resistivity profile and instability of the plane sheet pinch},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14686},
  year      = {1998},
  abstract  = {The stability of the quiescent ground state of an incompressible, viscous and electrically conducting fluid sheet, bounded by stress-free parallel planes and driven by an external electric field tangential to the boundaries, is studied numerically. The electrical conductivity varies as cosh-2(x1/a), where x1 is the cross-sheet coordinate and a is the half width of a current layer centered about the midplane of the sheet. For a <~ 0.4L, where L is the distance between the boundary planes, the ground state is unstable to disturbances whose wavelengths parallel to the sheet lie between lower and upper bounds depending on the value of a and on the Hartmann number. Asymmetry of the configuration with respect to the midplane of the sheet, modelled by the addition of an externally imposed constant magnetic field to a symmetric equilibrium field, acts as a stabilizing factor.},
  language  = {en}
}
@unpublished{RuedigerFeudelSeehafer1998,
  author    = {R{\"u}diger, Sten and Feudel, Fred and Seehafer, Norbert},
  title     = {Dynamo bifurcations in an array of driven convection-like rolls},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14678},
  year      = {1998},
  abstract  = {The bifurcations in a three-dimensional incompressible, electrically conducting fluid with an external forcing of the Roberts type have been studied numerically. The corresponding flow can serve as a model for the convection in the outer core of the Earth and is realized in an ongoing laboratory experiment aimed at demonstrating a dynamo effect. The symmetry group of the problem has been determined and special attention has been paid to symmetry breaking by the bifurcations. The nonmagnetic, steady Roberts flow loses stability to a steady magnetic state, which in turn is subject to secondary bifurcations. The secondary solution branches have been traced until they end up in chaotic states.},
  language  = {en}
}
@unpublished{ZienickeSeehaferFeudel1997,
  author    = {Zienicke, Egbert and Seehafer, Norbert and Feudel, Fred},
  title     = {Bifurcations in two-dimensional Rayleigh-B{\´e}nard convection},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14534},
  year      = {1997},
  abstract  = {Two-dimensional bouyancy-driven convection in a horizontal fluid layer with stress-free boundary conditions at top and bottom and periodic boundary conditions in the horizontal direction is investigated by means of numerical simulation and bifurcation-analysis techniques. As the bouyancy forces increase, the primary stationary and symmetric convection rolls undergo successive Hopf bifurcations, bifurcations to traveling waves, and phase lockings. We pay attention to symmetry breaking and its connection with the generation of large-scale horizontal flows. Calculations of Lyapunov exponents indicate that at a Rayleigh number of 2.3×105 no temporal chaos is reached yet, but the system moves nonchaotically on a 4-torus in phase space.},
  language  = {en}
}