Scaffolding Cognition with Words

We describe a set of experiments investigating the role of natural language symbols in scaffolding situated action. Agents are evolved to respond appropriately to commands in order to perform simple tasks. We explore three different conditions, which show a significant advantage to the re-use of a public symbol system, through self-cueing leading to qualitative changes in performance. This is modelled by looping spoken output via environment back to heard input. We argue this work can be linked to, and sheds new light on, the account of self-directed speech advanced by the developmental psychologist Vygotsky in his model of the development of higher cognitive function

The ESO Key-Programme ``A Homogeneous Bright QSO Survey'' - I The Methods and the ``Deep'' Fields

This is the first paper in a series aimed at defining a statistically significant sample of QSOs in the range $15 < B < 18.75$ and $0.3 < z < 2.2$. The selection is carried out using direct plates obtained at the ESO and UK Schmidt Telescopes, scanned with the COSMOS facility and searched for objects with an ultraviolet excess. Follow-up spectroscopy, carried out at ESO La Silla, is used to classify each candidate. In this initial paper, we describe the scientific objectives of the survey; the selection and observing techniques used. We present the first sample of 285 QSOs ($M_B < -23$) in a 153 deg$^2$ area, covered by the six ``deep'' fields, intended to obtain significant statistics down $B \simeq 18.75$ with unprecedented photometric accuracy. From this database, QSO counts are determined in the magnitude range $17 < B < 18.75$.Comment: 21 pages uuencoded compressed postscript, to appear in Astronomy and Astrophysics Supplements, 199

Melt-quenched porous organic cage glasses

The discrete molecular nature of porous organic cages (POCs) has allowed us to direct the formation of crystalline materials by crystal engineering. It has also been possible to create porous amorphous solids by deliberately disrupting the crystalline packing, either with chemical modification or by processing. More recently, organic cages were used to form isotropic porous liquids. However, the connection between solid and liquid states of POCs, and the glass state, are almost completely unexplored. Here, we investigate the melting and glass-forming behaviour of a range of organic cages, including both shapepersistent POCs formed by imine condensation, and reduced and synthetically post-modified amine POCs that are more flexible and lack shape-persistence. The organic cages exhibited melting and quenching of the resultant liquids provides molecular glasses. One of these molecular glasses exhibited improved gas uptake for both CO2 and CH4 compared to the starting amorphous cage. In addition, foaming of the liquid in one case resulted in a more stable and less soluble glass, which demonstrates the potential for an alternative approach to forming materials such as membranes without solution processing

A Search for OH Megamasers at z > 0.1. III. The Complete Survey

We present the final results from the Arecibo Observatory OH megamaser survey. We discuss in detail the properties of the remaining 18 OH megamasers detected in the survey, including 3 redetections. We place upper limits on the OH emission from 85 nondetections and examine the properties of 25 ambiguous cases for which the presence or absence of OH emission could not be determined. The complete survey has discovered 50 new OH megamasers (OHMs) in (ultra)luminous infrared galaxies ([U]LIRGs) which doubles the sample of known OHMs and increases the sample at z>0.1 sevenfold. The Arecibo OH megamaser survey indicates that the OHM fraction in LIRGs is an increasing function of the far-IR luminosity (L_{FIR}) and far-IR color, reaching a fraction of roughly one third in the warmest ULIRGs. Significant relationships between OHMs and their hosts are few, primarily due to a mismatch in size scales of measured properties and an intrinsic scatter in OHM properties roughly equal to the span of the dataset. We investigate relationships between OHMs and their hosts with a variety of statistical tools including survival analysis, partial correlation coefficients, and a principal component analysis. There is no apparent OH megamaser ``fundamental plane.'' We compile data on all previously known OHMs and evaluate the possible mechanisms and relationships responsible for OHM production in merging systems. The OH-FIR relationship is reexamined using the doubled OHM sample and found to be significantly flatter than previously thought: L_{OH} ~ L_{FIR}^{1.2 +/- 0.1}. This near-linear dependence suggests a mixture of saturated and unsaturated masers, either within individual galaxies or across the sample.Comment: 28 pages, 14 figures, accepted by AJ. (AASTeX, includes emulateapj5 and onecolfloat5

A slitless spectroscopic survey for quasars near quasars

We present the results of the Quasars near Quasars (QNQ) survey, a CCD-based slitless spectroscopic survey for faint V<22 quasars at 1.7<z<3.6 on 18 26.2'x33.5' fields centred on bright quasars at 2.76<z<4.69. In total 169 quasar candidates with emission lines were selected from the extracted flux-calibrated spectra on the basis of well-defined automatic selection criteria followed by visual inspection and verification. With follow-up spectroscopy of 81 candidates that were likely to reside at z>1.7 we were able to confirm 80 new quasars at 0.580<z<3.586 on 16 of our fields. 64 of the newly discovered quasars are located at z>1.7. The overall high success rate implies that most of the remaining 88 candidates are quasars as well, although the majority of them likely resides at z<1.7 on the basis of the observed line shapes and strengths. Due to the insufficient depth of the input source catalogues needed for extraction of the slitless spectra our survey is not well defined in terms of limiting magnitude for faint 2.5<z<3.6 quasars whose Lyman alpha emission is detectable well beyond V=22, albeit at a continuum S/N<1. While not useful for characterising the evolving space density of quasars, our sample provides many new closely spaced quasar sightlines around intensely studied quasars for further investigations on the three-dimensional distribution of the intergalactic medium.Comment: 18 pages, 16 figures, accepted by A&A, includes Table 2 from online material, full paper with appendices containing additional figures and tables available at http://www.aip.de/People/gworseck/qnqpaper/qnqpaper_final.pd

Talking South African fathers: a critical examination of men’s constructions and experiences of fatherhood and fatherlessness

The absence of biological fathers in South Africa has been constructed as a problem for children of both sexes but more so for boy-children. Arguably the dominant discourse in this respect has demonized non-nuclear, female-headed households. Fathers are constructed as either absent or ‘bad’. Thus it has become important to explore more closely how male care-givers have been experienced by groups of men in South Africa. This article examines discourses of fatherhood and fatherlessness by drawing on qualitative interviews with a group of 29 men who speak about their reported experiences and understandings of being fathered or growing up without biological fathers. Two major and intertwined subjugated discourses about adult men’s experiences of being fathered that counter- balance the prevailing discourses about meaning of fatherhood and fatherlessness became evident, namely, ‘being always there’ and ‘talking fatherhood’. The importance of the experience of fatherhood as ‘being there’, which relates to a quality of time and relationship between child and father rather than physical time together, is illustrated. It is not only biological fathers who can ‘be there’ for their sons but also social fathers, other significant male role models and father figures who step in at different times in participants’ lives when biological fathers are unavailable for whatever reason. Second, many positive experiences of fathers or father figures that resist a traditional role of authority and control and subscribe to more nurturant and non-violent forms of care, represented as ‘talking’ fathers, are underlined. If we are to better understand the impact of colonial and apartheid history and its legacy on family life in contemporary society, there is a need for more historically and contextually informed studies on the meaning of fatherhood and fatherlessness.Web of Scienc