Heavy elements in Galactic and Magellanic Cloud HII regions: recombination-line versus forbidden-line abundances

We have obtained deep optical, long-slit spectrophotometry of the Galactic HII regions M 17, NGC 3576 and of the Magellanic Cloud HII regions 30 Doradus, LMC N11B and SMC N66, recording the optical recombination lines (ORLs) of CII, NII and OII. Temperature-insensitive ORL C2+/O2+ and N2+/O2 ratios are obtained for all nebulae except SMC N66. The ORL C2+/O2+ ratios show remarkable agreement within each galactic system, while also being in agreement with the corresponding CEL ratios. For all five nebulae, the O2+/H+ abundance derived from multiple OII ORLs is found to be higher than the corresponding value derived from the strong [OIII] 4959, 5007A CELs, by factors of 1.8--2.7 for four of the nebulae. The LMC N11B nebula exhibits a more extreme discrepancy factor for the O2+ ion, ~5. Thus these HII regions exhibit ORL/CEL abundance discrepancy factors that are similar to those previously encountered amongst planetary nebulae. Our optical CEL O2+/H+ abundances agree to within 20-30 per cent with published O2+/H+ abundances that were obtained from observations of infrared fine-structure lines. Since the low excitation energies of the latter make them insensitive to variations about typical nebular temperatures, fluctuations in temperature are ruled out as the cause of the observed ORL/CEL O2+ abundance discrepancies. We present evidence that the observed OII ORLs from these HII regions originate from gas of very similar density (<3500 cm-3) to that emitting the observed heavy-element optical and infrared CELs, ruling out models that employ high-density ionized inclusions in order to explain the abundance discrepancy. We consider a scenario whereby much of the heavy-element ORL emission originates from cold (<=500 K) metal-rich ionized regions.Comment: 24 pages; 9 figures; accepted by Monthly Notices of the Royal Astronomical Societ

Making sense of theory construction: Metaphor and disciplined imagination

This article draws upon Karl Weick’s insights into the nature of theorizing, and extends and refines his conception of theory construction as ‘disciplined imagination’. An essential ingredient in Weick’s ‘disciplined imagination’ involves his assertion that thought trials and theoretical representations typically involve a transfer from one epistemic sphere to another through the creative use of metaphor. The article follows up on this point and draws out how metaphor works, how processes of metaphorical imagination partake in theory construction, and how insightful metaphors and the theoretical representations that result from them can be selected. The paper also includes a discussion of metaphors-in-use (organizational improvisation as jazz and organizational behavior as collective mind) which Weick proposed in his own writings. The whole purpose of this exercise is to theoretically augment and ground the concept of ‘disciplined imagination’, and in particular to refine the nature of thought trials and selection within it. In doing so, we also aim to provide pointers for the use of metaphorical imagination in the process of theory construction

Familie und Schule: zwei Orte der Erziehung.

B

Evidence for Type Ia Supernova Diversity from Ultraviolet Observations with the Hubble Space Telescope

We present ultraviolet (UV) spectroscopy and photometry of four Type Ia supernovae (SNe 2004dt, 2004ef, 2005M, and 2005cf) obtained with the UV prism of the Advanced Camera for Surveys on the Hubble Space Telescope. This dataset provides unique spectral time series down to 2000 Angstrom. Significant diversity is seen in the near maximum-light spectra (~ 2000--3500 Angstrom) for this small sample. The corresponding photometric data, together with archival data from Swift Ultraviolet/Optical Telescope observations, provide further evidence of increased dispersion in the UV emission with respect to the optical. The peak luminosities measured in uvw1/F250W are found to correlate with the B-band light-curve shape parameter dm15(B), but with much larger scatter relative to the correlation in the broad-band B band (e.g., ~0.4 mag versus ~0.2 mag for those with 0.8 < dm15 < 1.7 mag). SN 2004dt is found as an outlier of this correlation (at > 3 sigma), being brighter than normal SNe Ia such as SN 2005cf by ~0.9 mag and ~2.0 mag in the uvw1/F250W and uvm2/F220W filters, respectively. We show that different progenitor metallicity or line-expansion velocities alone cannot explain such a large discrepancy. Viewing-angle effects, such as due to an asymmetric explosion, may have a significant influence on the flux emitted in the UV region. Detailed modeling is needed to disentangle and quantify the above effects.Comment: 17 pages, 13 figures, accepted by Ap

The dimensions of prosociality: a cross-cultural lexical analysis

The West is usually portrayed as relatively individualistic. It is further argued that this tendency has influenced academia, leading to an underappreciation of the importance of prosociality. In the interest of exploring this topic, an enquiry was conducted into conceptualisations of prosociality across the world’s cultures. This enquiry focused on so-called untranslatable words, i.e., which lack an exact translation into another language (in this case, English). Through a quasi-systematic search of academic and grey literature, together with additional data collection, over 200 relevant terms were located. An adapted form of grounded theory identified five dimensions: socialising/congregating; morals/ethics; compassion/kindness; interaction/communication; and communality. The analysis sheds light on the dynamics of prosociality, as understood by cultures across the globe. Moreover, the roster of terms featured have the potential to enrich the nomological network in psychology, allowing for a richer conceptualisation of the social dimensions of human functioning

Introducing Time-to-Educate in a Job Search Model

Transition patterns from school to work differ considerably across OECD countries. Some countries exhibit high youth unemployment rates, which can be considered an indicator of the difficulty facing young people trying to integrate into the labor market. At the same time, education is a time-consuming process, and enrolment and dropout decisions depend on expected duration of studies, as well as on job prospects with and without completed degrees. One way to model entry into the labor market is by means of job search models, where the job arrival hazard is a key parameter in capturing the ease or difficulty in finding a job. Standard models of job search and education assume that skills can be upgraded instantaneously (and mostly in the form of on-the-job training) at a fixed cost. This paper models education as a time-consuming process, a concept which we call time-to-educate, during which an individual faces the trade-off between continuing education and taking up a job

Interpersonal communication

xxii, 238 p.; 23 cm

Socialization/ Danziger

175 hal.; 18 cm