Inszenierung und Verortung von Identität in der computervermittelten Kommunikation: rahmenanalytische Überlegungen am Beispiel des Online-Chat

'Auf der Grundlage einer explorativen Studie über das 'Online-Chatten' und bezugnehmend auf die Goffmansche 'Rahmen-Analyse' werden im vorliegenden Beitrag einige der Strategien herausgearbeitet, mit denen die Teilnehmer eines 'Online-Chats' versuchen - trotz der medialen Restriktionen - soziale Interaktionsprozesse herzustellen und zu bewältigen. Am Beispiel des Umgangs der NutzerInnen mit dem Problem der Präsentation und Verortung von Identität im Chat lässt sich zeigen, wie sich die Teilnehmer im Zuge aktiver Aneignungsprozesse neue interaktionsrelevante Orientierungsmöglichkeiten und Kontextinformationen konstruieren, um kommunikative Beziehungen auch in einem auf den Computerbildschirm beschränkten gemeinsamen Wahrnehmungsraum koordinieren zu können. Hierfür müssen sich die Teilnehmer sowohl spezifische (selbst-)darstellerische Fähigkeiten aneignen, als auch Kompetenzen dahingehend ausbilden, den Interaktionspartner anhand der im Chat verfügbaren Verortungsmerkmale einzuschätzen und einzuordnen.'(Autorenreferat

The International Civic and Citizenship Education Study: Extent and variation of lower-secondary students’ civic knowledge, and changes since 2009

The IEA International Civic and Citizenship Education Study (ICCS) investigated the preparedness and preparation of young people to ‘undertake their roles as citizens in a range of countries’ (Schulz et al., 2017, p xv). ICCS 2016 is the second cycle of ICCS with the first cycle of ICCS having been completed in 2009. In ICCS, the preparedness of young people to participate is operationalized through measures of ‘students’ knowledge and understanding of civics and citizenship as well as students’ attitudes, perceptions, and activities related to civics and citizenship (Schulz et al., 2017 p 1). Students’ knowledge and understanding of civics and citizenship was measured using a paper-based test and the results are reported on a single scale of ‘civic knowledge’ in ICCS (Schulz et al., 2016, Schulz et al., 2010). This paper describes variations in student civic knowledge as measured in ICCS, including the relationship between selected student characteristics and civic knowledge and, comparisons between civic knowledge of students in 2016 and that of students in ICCS 2009

The contact of graphene with Ni(111) surface: description by modern dispersive forces approaches

Here we present a Density Functional Theory (DFT) study on the suitability of modern corrections for the inclusion of dispersion related terms (DFT-D) in treating the interaction of graphene and metal surfaces, exemplified by the graphene/Ni(111) system. The Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional is used as basis, on top of which we tested the family of Grimme corrections (D2 and D3, including Becke-Jonson damping and Andersson approach) as well as different flavors of the approach by Tkatchenko and Scheffler (TS). Two experimentally observed chemisorbed states, top-fcc and bridge-top conformations, were examined, as well as one physisorbed situation, the hcp-fcc state. Geometric, energetic, and electronic properties were compared to sets of experimental data for our model system of graphene/Ni(111), but also for available data of bulk Ni, graphite, and free-standing graphene. Results show that two of the most recent approximations, the fully ab initio TS-MBD, and the semi-empirical Grimme D3 correction are best suited to describe graphene↔metal contacts, yet, comparing to earlier studies, the Rev-vdW-DF2 functional is also a good option, whereas optB86-vdW and optB88b-vdW functionals are fairly close to experimental values to be harmless used. The present results highlight how different approaches for the approximate treatment of dispersive forces yield different results, and so fine-tuning and testing of the envisioned approach for every specific system is advisable. The present survey clears the path for future accurate and affordable theoretical studies of nanotechnologic devices based on graphene-metal contacts

Large-area epitaxial growth of curvature-stabilized ABC trilayer graphene.

The properties of van der Waals (vdW) materials often vary dramatically with the atomic stacking order between layers, but this order can be difficult to control. Trilayer graphene (TLG) stacks in either a semimetallic ABA or a semiconducting ABC configuration with a gate-tunable band gap, but the latter has only been produced by exfoliation. Here we present a chemical vapor deposition approach to TLG growth that yields greatly enhanced fraction and size of ABC domains. The key insight is that substrate curvature can stabilize ABC domains. Controllable ABC yields ~59% were achieved by tailoring substrate curvature levels. ABC fractions remained high after transfer to device substrates, as confirmed by transport measurements revealing the expected tunable ABC band gap. Substrate topography engineering provides a path to large-scale synthesis of epitaxial ABC-TLG and other vdW materials

Transient growth and coupling of vortex and wave modes in self-gravitating gaseous discs

Flow nonnormality induced linear transient phenomena in thin self-gravitating astrophysical discs are studied in the shearing sheet approximation. The considered system includes two modes of perturbations: vortex and (spiral density) wave. It is shown that self-gravity considerably alters the vortex mode dynamics -- its transient (swing) growth may be several orders of magnitude stronger than in the non-self-gravitating case and 2-3 times larger than the transient growth of the wave mode. Based on this finding, we comment on the role of vortex mode perturbations in a gravitoturbulent state. Also described is the linear coupling of the perturbation modes, caused by the differential character of disc rotation. The coupling is asymmetric -- vortex mode perturbations are able to excite wave mode ones, but not vice versa. This asymmetric coupling lends additional significance to the vortex mode as a participant in spiral density waves and shocks manifestations in astrophysical discs.Comment: 10 pages, 8 figure

Host Galaxies of Luminous Type 2 Quasars at z ~ 0.5

We present deep Gemini GMOS optical spectroscopy of nine luminous quasars at redshifts z ~ 0.5, drawn from the SDSS type 2 quasar sample. Our targets were selected to have high intrinsic luminosities (M_V < -26 mag) as indicated by the [O III] 5007 A emission-line luminosity (L_[O III]). Our sample has a median black hole mass of ~ 10^8.8 M_sun inferred assuming the local M_BH-sigma_* relation and a median Eddington ratio of ~ 0.7, using stellar velocity dispersions sigma_* measured from the G band. We estimate the contamination of the stellar continuum from scattered quasar light based on the strength of broad H-beta, and provide an empirical calibration of the contamination as a function of L_[O III]; the scattered light fraction is ~ 30% of L_5100 for objects with L_[O III] = 10^9.5 L_sun. Population synthesis indicates that young post-starburst populations (< 0.1 Gyr) are prevalent in luminous type 2 quasars, in addition to a relatively old population (> 1 Gyr) which dominates the stellar mass. Broad emission complexes around He II 4686 A with luminosities up to 10^8.3 L_sun are unambiguously detected in three out of the nine targets, indicative of Wolf-Rayet populations. Population synthesis shows that ~ 5-Myr post-starburst populations contribute substantially to the luminosities (> 50% of L_5100) of all three objects with Wolf-Rayet detections. We find two objects with double cores and four with close companions. Our results may suggest that luminous type 2 quasars trace an early stage of galaxy interaction, perhaps responsible for both the quasar and the starburst activity.Comment: 20 pages, 13 figures, 7 tables; accepted to Ap

Les ateliers du hameau Les Noires Terres à Messein (Meurthe-et-Moselle, Lorraine, France) :

L’occupation altomédiévale (VIe-VIIIe s.) au lieu-dit Les Noires Terres sur la commune de Messein, au sud de Nancy (Meurthe-et-Moselle, France, fouille 2003-2004), associe des unités composées d’un bâtiment d’habitation et de structures de type agricole (greniers, silos, enclos, cabanes excavées…) à des ateliers de production et de travail du fer (préparation du minerai, fabrication du charbon de bois, fourneaux de réduction, forgeage du fer). La présence des déchets relevant d’une chaîne opératoire complète (de la préparation du minerai à l’élaboration de produits finis), documentée par l’étude paléométallurgique, ainsi que le volume de production estimé au vu de leur quantité (plusieurs dizaines de tonnes de fer), suggèrent qu’il s’agit de l’activité principale des occupants et non pas d’une activité d’appoint aux pratiques agricoles. La nature de l’occupation est donc discutée : les vestiges découverts correspondraient aux unités d’habitation d’artisans spécialisés, avec leurs ateliers, comportant l’ensemble des installations et équipements nécessaires à leur subsistance et à leur vie quotidienne. On peut ainsi émettre l’hypothèse qu’il s’agit d’une des formes d’organisation de la production du fer dans le monde franc au cours du premier Moyen Âge, et qu’elle correspond peut-être à ce que nous laissent entrevoir les polyptiques de la période carolingienne.The Altomedieval occupation (6th-8th c.) at Les Noires Terres in Messein, to the south of Nancy (Meurthe-et-Moselle, France, excavation 2003-2004), associates elements composed of a dwelling and agricultural structures (granaries, silos, enclosures, excavated huts, etc.) with iron production and transformation workshops (iron ore preparation, wood charcoal production, reduction furnaces, iron forging). The presence of waste products corresponding to a complete chaîne opératoire (production sequence) (from iron ore preparation to finished products), documented by the paleo-metallurgical study and the production volume estimated from their quantity (several dozen tons of iron), suggest that this was the main activity of the occupants, rather than an activity secondary to agricultural activities. The nature of the occupation is thus discussed : the remains discovered could correspond to the dwellings of the specialized artisans, with their workshops, including all the installations and equipment necessary for their subsistence and daily life. We can thus propose the hypothesis that this was one of the forms of iron production organization employed by the Franks during the Early Middle Ages, and that if might correspond to that which is suggested by the polyptyques of the Carolingian period.Die frühmittelalterliche Besiedlung (6.-8. Jh.) von Les Noires Terres auf dem Gebiet der Gemeinde Messein, südlich von Nancy (Departement Meurthe-et-Moselle, Frankreich, Ausgrabung 2003-2004), besteht aus Siedlungseinheiten, die sich jeweils aus einem Wohnbau mit landwirtschaftlichen Einrichtungen (Speicherbauten, Silos, Einfriedungen, Grubenhäuser…) und Werkstätten für die Eisengewinnung und -verarbeitung (Erzaufbereitung, Holzkohlengewinnung, Rennöfen, Eisenschmieden) zusammensetzen. Die Abfälle, die von einem kompletten, durch die paläometallurgische Studie dokumentierten Verhüttungsprozess (von der Erzaufbereitung bis hin zur Formgebung der Endprodukte) zeugen, sowie das anhand der Abfälle geschätzte Produktionsvolumen (mehrere Dutzend Tonnen Eisen) legen nahe, dass es sich hier um die Hauptbeschäftigung der Bewohner handelte und nicht um eine Nebentätigkeit. Demzufolge steht die Art der Besiedlung zur Diskussion: Die Funde und Befunde würden einer auf die Eisengewinnung und -verarbeitung spezialisierte Handwerkersiedlung entsprechen mit allen für die Arbeit und den Alltag der Bewohner notwendigen Anlagen und Einrichtungen, Wohnhäusern und Werkstätten. So können wir die Hypothese vorlegen, dass es sich um eine der Organisationsformen der frühmittelalterlichen fränkischen Eisenmetallurgie handelt, welche die Urbare der karolingischen Periode erahnen lassen

Fast Growth of Supermassive Black Holes in Galaxies

We report on a calculation of the growth of the mass of supermassive black holes at galactic centers from dark matter and Eddington - limited baryonic accretion. Assuming that dark matter halos are made of fermions and harbor compact degenerate Fermi balls of masses from $10^{3}M_{\odot}$ to $10^{6}M_{\odot}$, we find that dark matter accretion can boost the mass of seed black holes from about $\sim 5M_{\odot}$ to $10^{3-4}M_{\odot}$ black holes, which then grow by Eddington - limited baryonic accretion to supermassive black holes of $10^{6 - 9}M_{\odot}$. We then show that the formation of the recently detected supermassive black hole of $3\times 10^{9}M_{\odot}$ at a redshift of $z = 6.41$ in the quasar SDSS J114816.64+525150.3 could be understood if the black hole completely consumes the degenerate Fermi ball and then grows by Eddington - limited baryonic accretion. In the context of this model we constrain the dark matter particle masses to be within the range from 12 ${\rm keV/c}^{2}$ to about 450 ${\rm keV/c}^{2}$. Finally we investigate the black hole growth dependence on the formation time of the seed BH and on the mass of the seed BH. We find that in order to fit the observed data point of $M_{BH} \sim 3 \times 10^{9}M_{\odot}$ and $z \sim 6.41$, dark matter accretion cannot start later than about $2 \times 10^{8}$ years and the seed BH cannot be greater than about $10^{4}M_{\odot}$. Our results are in full agreement with the WMAP observations that indicate that the first onset of star formation might have occurred at a redshift of $z \sim 15 - 20$. For other models of dark matter particle masses, corresponding constraints may be derived from the growth of black holes in the center of galaxies.Comment: New black hole growth mechnism, references added, 13 pages, accepted for publication in Astronomy & Astrophysics Journa

Reliability and accuracy of single-molecule FRET studies for characterization of structural dynamics and distances in proteins

Single-molecule Förster-resonance energy transfer (smFRET) experiments allow the study of biomolecular structure and dynamics in vitro and in vivo. We performed an international blind study involving 19 laboratories to assess the uncertainty of FRET experiments for proteins with respect to the measured FRET efficiency histograms, determination of distances, and the detection and quantification of structural dynamics. Using two protein systems with distinct conformational changes and dynamics, we obtained an uncertainty of the FRET efficiency ≤0.06, corresponding to an interdye distance precision of ≤2 Å and accuracy of ≤5 Å. We further discuss the limits for detecting fluctuations in this distance range and how to identify dye perturbations. Our work demonstrates the ability of smFRET experiments to simultaneously measure distances and avoid the averaging of conformational dynamics for realistic protein systems, highlighting its importance in the expanding toolbox of integrative structural biology