Is communication via the internet public communication?

Die Medien- und Kommunikationswissenschaft stellt sich im Zuge der Medienentwicklung beständig neue Fragen im Spannungsfeld zwischen Stabilität und Wandel der gesellschaftlichen Kommunikation. Es existieren dabei viele relevante Themenfelder, zu denen es noch keine Publikationen gibt, die systematisch abwägen würden, was wir bisher (empirisch und nicht-empirisch) wissen und welche Schlüsse aus diesem gebündelten Wissen zu ziehen sind. Dieser Band soll systematisch Antworten auf wichtige aktuelle oder dauerhaft relevante Fragen des Fachs geben, indem sich die Beiträge ganz auf die Auseinandersetzung mit einer konkreten Frage konzentrieren und so Raum für eine gründliche Argumentation bleibt. Der Band ist dem Andenken von Professor Wolfram Peiser gewidmet. Mit Beiträgen von Hans-Bernd Brosius, Felix Frey, Romy Fröhlich, Christina Holtz-Bacha, Benjamin Krämer, Philipp Müller, Christoph Neuberger, Carsten Reinemann, Anna-Luisa Sacher, Johanna Schindler, Klaus Schönbach und Cornelia Wallner

Color-Octet Contributions to J/psi Photoproduction via Fragmentation at HERA

We study J/psi photoproduction via fragmentation at next-to-leading order in the QCD-improved parton model, using the nonrelativistic factorization formalism proposed by Bodwin, Braaten, and Lepage. We consider direct and resolved photoproduction of prompt J/psi mesons and chi_{cJ} mesons radiatively decaying to J/psi+gamma, taking into account the formation of both color-singlet and color-octet c anti-c states. Adopting the values of the long-distance color-octet matrix elements extracted from fits to prompt-J/psi data recently taken at the Fermilab Tevatron, we predict that measurements of J/psi photoproduction at DESY HERA should show a distinctive excess over the expectation based on the color-singlet model at small values of the inelasticity variable z. This is complementary to the expected enhancement at z close to 1 due to the color-octet contribution to photon-gluon fusion.Comment: 10 pages (Latex), 3 figures (Postscript

Phenolsäuregehalte und antioxidative Kapazität in Wurzelextrakten von Salvia miltiorrhiza Bunge

In den Jahren 2008-2009 wurden in der Versuchsstation Groß-Gerau (Sandboden) Feldversuche mit Chinesischem Salbei durchgeführt. Die erzielten Ergebnisse bringen zum Ausdruck, dass die Gehalte an Salvianolsäure B und Rosmarinsäure sowie die antioxidative Kapazität signifikant durch den Erntetermin beeinflusst sind. Die Gehalte beider Phenolcarbonsäuren und die antioxidative Kapazität waren im Frühjahr nach der Überwinterung des Salbeis deutlich höher als in den Herbstmonaten. Der höchste Gehalt an Salvianolsäure B wurde im Frühjahr (28. 04. 2009) mit einem Mittelwert von 5,26 % erreicht. Die Ergebnisse belegen, dass Salvianolsäure B am stärsten zur antioxidativen Kapzität in den Salbeiwurzeln beiträgt. Einen weiteren Beitrag zur antioxidativen Kapazität leisten auch die Rosmarinsäure und das Tanshinon I. Stichwörter: Salvia miltiorrhiza, Salvianolsäure B. Rosmarinsäure, Tanshinone, antioxidative KapazitätPhenolic acid contents and antioxidant capacity in root extracts of Salvia miltiorrhiza BungeIn 2008-2009 field experiments with Salvia miltiorrhiza were carried out in the research station Gross-Gerau (sand soil). The received data show that the contents of salvianolic acid B, rosmarinic acid and antioxidant capacity significantly depend on the harvest time of S. miltiorrhiza. Content of both phenolic acids and antioxidant capacity were significantly higher in spring after overwintering than in autumn. The highest level of salvianolic acid B was reached in spring with an average of 5.26 % dry matter. The results show that salvianolic acid B contributes most to enhancing antioxidant capacity in root extracts of S. miltiorrhiza. Rosmarinic acid and tanshinon I provide another contribution to antioxidative capacity. Keywords: Salvia miltiorrhiza, salvianolic acid B, rosmarinic acid, tanshinones, antioxidant capacit

Coupling aerosols to (cirrus) clouds in the global EMAC-MADE3 aerosol–climate model

A new cloud microphysical scheme including a detailed parameterization for aerosol-driven ice formation in cirrus clouds is implemented in the global ECHAM/MESSy Atmospheric Chemistry (EMAC) chemistry–climate model and coupled to the third generation of the Modal Aerosol Dynamics model for Europe adapted for global applications (MADE3) aerosol submodel. The new scheme is able to consistently simulate three regimes of stratiform clouds – liquid, mixed-, and ice-phase (cirrus) clouds – considering the activation of aerosol particles to form cloud droplets and the nucleation of ice crystals. In the cirrus regime, it allows for the competition between homogeneous and heterogeneous freezing for the available supersaturated water vapor, taking into account different types of ice-nucleating particles, whose specific ice-nucleating properties can be flexibly varied in the model setup. The new model configuration is tuned to find the optimal set of parameters that minimizes the model deviations with respect to observations. A detailed evaluation is also performed comparing the model results for standard cloud and radiation variables with a comprehensive set of observations from satellite retrievals and in situ measurements. The performance of EMAC-MADE3 in this new coupled configuration is in line with similar global coupled models and with other global aerosol models featuring ice cloud parameterizations. Some remaining discrepancies, namely a high positive bias in liquid water path in the Northern Hemisphere and overestimated (underestimated) cloud droplet number concentrations over the tropical oceans (in the extratropical regions), which are both a common problem in these kinds of models, need to be taken into account in future applications of the model. To further demonstrate the readiness of the new model system for application studies, an estimate of the anthropogenic aerosol effective radiative forcing (ERF) is provided, showing that EMAC-MADE3 simulates a relatively strong aerosol-induced cooling but within the range reported in the Intergovernmental Panel on Climate Change (IPCC) assessments

J/psi Inclusive Production in ep Deep-Inelastic Scattering at DESY HERA

We calculate the cross section of J/psi plus jet associated production in ep deep-inelastic scattering within the factorization formalism of nonrelativistic quantum chromodynamics. Our analytic results disagree with previous analyses, both for the colour-singlet and colour-octet channels. Our theoretical predictions agree reasonably well with recent data taken by the H1 Collaboration at DESY HERA, significantly better than those obtained within the colour-singlet model.Comment: 27 pages (Latex), 9 figures (Postscript), to appear in Nucl. Phys.

Charmonium Production via Fragmentation at DESY HERA

The cross section for the photoproduction of large-p_T J/psi mesons at HERA is calculated at next-to-leading order, adopting a perturbative approach to describe the fragmentation of charm quarks and gluons into J/psi mesons. We treat the charm quark according to the massless factorization scheme, where it is assumed to be one of the active flavours inside the proton and the resolved photon. We present inclusive distributions in transverse momentum and rapidity, including the contributions due to direct and resolved photons. The importance of the colour-octet components of the J/psi wave function, which contribute to the fragmentation process, is emphasized. In addition to prompt J/psi production, we consider also the production of chi_{cJ} states followed by radiative decays to J/psi mesons, both in the colour-singlet and colour-octet channels.Comment: 32 pages (Latex), 12 figures (Postscript

J/psi Inclusive Production in nu N Neutral-Current Deep-Inelastic Scattering

We calculate the cross section of J/psi inclusive production in neutrino-nucleon deep-inelastic scattering via the weak neutral current within the factorization formalism of nonrelativistic quantum chromodynamics. Besides J/psi single production via the Z-gluon fusion mechanism, we also consider J/psi plus hadron-jet associated production. We take into account both direct production and feed-down from directly-produced heavier charmonia. We present theoretical predictions for the J/psi transverse-momentum and rapidity distributions, which can be measured in the CHORUS and NOMAD experiments at CERN, including conservative error estimates. In order to interpret a recent CHORUS measurement of the total cross section, we also estimate the contribution due to J/psi prompt production via diffractive processes using the vector-meson dominance model.Comment: 34 pages (Latex), 5 figures (Postscript); significantly extended to include feed-down and diffractive contributions and nuclear corrections; accepted for publication in Nucl. Phys.

Evidence for Colour-Octet Mechanism from CERN LEP2 gamma gamma -> J/psi + X Data

We present theoretical predictions for the transverse-momentum distribution of J/psi mesons promptly produced in gamma gamma collisions within the factorization formalism of nonrelativistic quantum chromodynamics, including the contributions from both direct and resolved photons, and we perform a conservative error analysis. The fraction of J/psi mesons from decays of bottom-flavoured hadrons is estimated to be negligibly small. New data taken by the DELPHI Collaboration at LEP2 nicely confirm these predictions, while they disfavour those obtained within the traditional colour-singlet model.Comment: 11 pages (Latex), 3 figures (Postscript); updated experimental data included, references added, accepted for publication in Phys. Rev. Let