The infrared spectra of very large, compact, highly symmetric, polycyclic aromatic hydrocarbons (PAHs)

The mid-infrared spectra of large PAHs ranging from C54H18 to C130H28 are determined computationally using Density Functional Theory. Trends in the band positions and intensities as a function of PAH size, charge and geometry are discussed. Regarding the 3.3, 6.3 and 11.2 micron bands similar conclusions hold as with small PAHs. This does not hold for the other features. The larger PAH cations and anions produce bands at 7.8 micron and, as PAH sizes increases, a band near 8.5 micron becomes prominent and shifts slightly to the red. In addition, the average anion peak falls slightly to the red of the average cation peak. The similarity in behavior of the 7.8 and 8.6 micron bands with the astronomical observations suggests that they arise from large, cationic and anionic PAHs, with the specific peak position and profile reflecting the PAH cation to anion concentration ratio and relative intensities of PAH size. Hence, the broad astronomical 7.7 micron band is produced by a mixture of small and large PAH cations and anions, with small and large PAHs contributing more to the 7.6 and 7.8 micron component respectively. For the CH out-of-plane vibrations, the duo hydrogens couple with the solo vibrations and produce bands that fall at wavelengths slightly different than their counterparts in smaller PAHs. As a consequence, previously deduced PAH structures are altered in favor of more compact and symmetric forms. In addition, the overlap between the duo and trio bands may reproduce the blue-shaded 12.8 micron profile.Comment: ApJ, 36 pages, 9 fig

The impact of preschool feeding programmes on the growth of disadvantaged young children in developing countries: a systematic review of randomised trials

Background: Childhood malnutrition in developing countries contributes to developmental delays, as well as increased morbidity and mortality. The effectiveness of feeding programmes as a strategy to improve childhood malnutrition has been questioned.Objective: A systematic review was undertaken to examine the effectiveness of preschool feeding programmes in fostering the growth of children in developing countries.Design: A systematic literature search was undertaken to identify published studies that related to the objective. Studies had to be randomised intervention studies that reported on the growth outcomes of children from birth to six years of age in order to be included.Setting: An initial literature search yielded 59 studies, of which 44 were excluded based on initial screening. Five more were omitted based on detailed data extraction. Ten studies met the inclusion criteria. The results of these studies were compared and narratively described in the context of the objective.Results: The studies showed a great level of heterogeneity with regard to sample characteristics, intervention and reporting of results. In the context of recovery from malnutrition, most studies reported there to be a positive effect from feeding programmes. In studies that reported on weight gain, those that employed a supervised intake of food supplements resulted in higher rates of weight gain. Micronutrient fortification was described as having a positive influence on the rate of linear growth in studies that reported on linear growth. Intensive nutrition education aimed at mothers and caregivers is a sustainable way in which to change child feeding behaviour and may contribute to the effectiveness of nutrition intervention.Conclusion: The limitations of the study included the following: there was a low number (59) of identified studies in the initial search because of the use of limited search terms, assessment of risk of bias was carried out by only one reviewer using a self-designed grading system, there were high levels of heterogeneity, and less than half of the individual studies were  rated to be of a high quality. In view of these limitations, no firm conclusion can be drawn. Additional research, aimed at determining the impact of supplementary feeding programmes in supporting the growth of disadvantaged children, is encouraged.Keywords: preschool feeding programmes, growth, disadvantaged children, developing countrie

Informative assessment: A supportive tool for systemic validity in language education

AbstractAccountability in language testing is normally supported through a validation process. In language teaching, however, the matter of accountability is sometimes overlooked, especially when the focus falls on curriculum completion. In view of the reciprocity that exists between language teaching and testing, core principles used for test validation are also useful for ensuring accountability in course design. This paper evaluates a language course offered to Education students at a tertiary institution by drawing on the notions of construct and content validity. Empirical data gleaned from a literacy survey and assessment artefacts are interpreted against course objectives and content. A need is identified for substantial revisions to the course in order to ensure closer alignment with students’ language learning needs. The study shows how accountability in language education coheres with the principle of systemic validity and the relevance of analysing and correlating different kinds of data

Magnetic Bound States in Dimerized Quantum Spin Systems

Magnetic bound states are a general phenomenon in low dimensional antiferromagnets with gapped singlet states. Using Raman scattering on three compounds as dedicated examples we show how exchange topology, dimensionality, defects and thermal fluctuations influence the properties and the spectral weight of these states.Comment: 3 pages, 1 figure, proceedings of the SCES'98, Paris, to be published in Physica

The protection of personal and medical data - a call for confidentiality

Personal data and privacy are increasingly being threatened by a boom in technological development - the replacement of conventional networks of communication with the perfected combination of computer and telecommunications. The subsequent high degree of transparency has the potential to damage the individual's right to 'informational self-determination'. The most common ways of unlawfully entering a computer data system, the reasons why an individual's information is treated as confidential and the ethical issues involved, international and local statutory instruments that protect such personal information, and ways to stop the outflow of personal information are discussed

Contextualizing South Africa’s participation in the SITES 2006 module

The International Association for the Evaluation of Educational Achievement (IEA) initiated the Second International Technology in Education Study (SITES 2006) — a large-scale comparative survey on the use of Information and Communication Technologies (ICTs) in schools. The goal was to understand the pedagogical use of ICTs in schools in 22 education systems. We aim to contextualize South Africa’s participation in SITES 2006 on four levels: (i) the nature and structure of the South African education system, (ii) a review of South Africa’s participation in SITES 2006, (iii) ICT infrastructure, facilities and equipment, and (iv) teachers’ use of ICTs for teaching and learning. SITES 2006 administered three questionnaires to school principals, technology coordinators, and mathematics and science teachers. The final sample consisted of 666 mathematics and 622 science teachers. Although most education systems collected data via the internet, South Africa was the only country that used only a paper-and-pencil data collection strategy with an average return rate of 90%. South Africa scored low on most variables, e.g. ICT infrastructure, facilities, and equipment. A large percentage of South African teachers reported their ICT incompetence. South Africa’s inability to cross the boundaries of traditional learning towards the development of 21st century teaching and learning skills inhibits social and economic growth for the development of human capital.Keywords: developing context; e-Education; ICT in education; large-scale study; mathematics education; science education; SITES 2006; South Africa

Investigating the impact of a combined approach of perceived organisational support for strengths use and deficit correction on employee outcomes

Orientation: The positive psychology paradigm suggests a balanced focus on employee strengths and deficits. However, an overemphasis on strengths has raised questions regarding the value of a focus on strengths use, deficit improvement or a combined approach with a balanced focus on both. Research purpose: The primary objective was to examine whether perceived organisational support (POS) for strengths use, POS for deficit improvement or a combined approach would be the strongest predictor of work engagement, learning, job satisfaction and turnover intention. Motivation for the study: In the literature, there is little empirical evidence to support an approach where both employees’ strengths are used and their deficits improved. Research design, approach and method: This study was conducted among 266 teachers from four public schools in the Western Cape. A cross-sectional survey design was used. Main findings: The results suggest that both strengths use and deficit improvement are important predictors of work engagement, learning, job satisfaction and turnover intention. Learning was higher and turnover intention lower for individuals experiencing a combined approach compared to those believing that their school did not support them in either using their strengths or improving their deficits. Furthermore, a combined approach was associated with higher job satisfaction than a strengths-based approach, and a deficit-based approach was shown to be associated with higher levels of work engagement and lower turnover intentions compared to an environment where neither employees’ strengths nor deficits were addressed. Practical or managerial implications: The results urge organisations to invest an equal amount of resources in their employees’ strengths and deficits, as opposed to neglecting either one. Such a combined approach may be associated with increased work engagement, learning and job satisfaction and lower turnover intention. Contribution: This study provides empirical evidence that supports a combined approach where both employees’ strengths are used and their deficits developed

2.5 V 35 dBm IIP3 75 MHz sixth-order active RC filter

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