Class size, pupil attentiveness and peer relations

BACKGROUND: Despite a long-running debate over the effects of class size differences on educational performance there is little evidence on the classroom processes that might be involved. AIMS: The effects of class size differences are examined in relation to social and behavioural adjustment to school, in terms of two dimensions: attentiveness and peer relations. It was predicted that as class size increased there would be more inattentiveness in class and more signs of social difficulties between children in the form of more rejection, asocial, anxious and aggressive behaviour, and less prosocial behaviour. SAMPLES: Data came from a large-scale longitudinal study of children over KS1 (4-7 years). The observation study was based on a subsample of 235 children in 21 small (average 19 children) and 18 large (average 33 children) reception classes (aged 5 years). The PBR sample involved over 5,000. METHODS: There were two complementary methods of data collection: first, a systematic observation study of pre-selected target children in terms of three 'social modes' - when with their teachers, other children and when not interacting - and in terms of work, procedural, social and off-task activities; and, second, a teacher administered Pupil Behaviour Rating (PBR) scale comprising over 50 items rated on a 3-point scale grouped into six 'factors': hyperactive/distractible, aggressive, anxious/ fearful, prosocial, asocial, and excluded. RESULTS: Observations showed that children in large classes were more likely to show off-task behaviour of all kinds, and more likely to interact with their peers in terms of off-task behaviour, social, and also on-task behaviours. Connections between class size and PBR factors were not strong. There was no support for the view that peer relations are better in smaller classes; indeed, there was a slight tendency for worse peer relations, in terms of aggression, asocial and excluded, in the smallest classes. CONCLUSIONS: There was confirmation that children in large classes are more distracted from work and more often off task. The unexpected result, based on teacher ratings, that small classes may lead to less social and more aggressive relations between children is discussed, along with implications for teachers of a tendency for more peer-related contacts in large classes

Relationships between class size and teaching: a multi-method analysis of English infant schools

Research and debate on class size differences has focused on relations with achievement, and there is little relevant research on what mediating classroom processes might be involved. In this article we investigate connections between class size and teaching interactions. We adopt a multimethod approach, integrating qualitative in formation from teachers' end-of-year accounts and data from case studies with quantitative information from time-allocation estimates and systematic observations. Our data come from a longitudinal study of two cohorts of more than 10,000 children altogether for 3 years after enrollment in English infant schools (aged 4-7 years). Our results show, overall, that in smaller classes there is more individualized teacher support for learning. We interpret the results in the context of teacher time allocation, research on effective teaching, and post-Vygotskian approaches to teaching. It is suggested that direct models of teacher influences on pupils need to be adapted to allow for class size as a contextual factor that influences both teachers and pupils

Pion Photoproduction Amplitude Relations in the 1/N_c Expansion

We derive expressions for pion photoproduction amplitudes in the 1/N_c expansion of QCD, and obtain linear relations directly from this expansion that relate electromagnetic multipole amplitudes at all energies. The leading-order relations in 1/N_c compare favorably with available data, while the next-to-leading order relations seem to provide only a small improvement. However, when resonance parameters are compared directly, the agreement at O(1/N_c) or O(1/N_c^2) is impressive.Comment: 19 pages, ReVTeX, 50 eps files combine into 5 compound figure

Imaginary in all directions: an elegant formulation of special relativity and classical electrodynamics

A suitable parameterization of space-time in terms of one complex and three quaternionic imaginary units allows Lorentz transformations to be implemented as multiplication by complex-quaternionic numbers rather than matrices. Maxwell's equations reduce to a single equation.Comment: 8 page

Contemplations on Dirac's equation in quaternionic coordinates

A formulation of Dirac's equation using complex-quaternionic coordinates appears to yield an enormous gain in formal elegance, as there is no longer any need to invoke Dirac matrices. This formulation, however, entails several peculiarities, which we investigate and attempt to interpret

Reactive halogens (BrO and OClO) detected in the plume of Soufrière Hills Volcano during an eruption hiatus

Volcanic plumes are sites of dynamic chemistry involving halogen gases. Here we present new data on the relative abundances of SO2, BrO and OClO gases emitted from Soufrière Hills Volcano [SHV). They were collected during an eruptive hiatus but during sustained degassing at this halogen-rich volcano. By comparison with data from a previous study during an eruptive phase and application of the data and modeling of Villemant et al. (2008), we suggest that, after consideration of errors, either the rate of HBr conversion to BrO is variable, ranging from ∼30% to ∼15%, and/or the relative partitioning of Cl and Br into the gas phase from the melt changes according to eruptive activity. We examine the potential implications of this for fluid-melt partitioning, and compare our results with data from the experimental literature. Our work contributes toward understanding the controls on the BrO/SO2 ratio for volcano monitoring purposes; the changes in plume chemistry with regard to bromine at the onset of lava extrusion may be large and rapid. OClO was detected in the plume at SHV for the first time. This species has only previously been detected in emissions from Mount Etna (using ground-based methods) and from Puyehue Cordon Caulle (using satellite-based methods). No HCHO or NOy species were detected in the spectra.The MVO is thanked for support during fieldwork. This work was also supported by the UK National Centre for Earth Observation (“Dynamic Earth and Geohazards"; http://comet.nerc.ac.uk).This is the final published version. It's also available from Wiley at http://onlinelibrary.wiley.com/doi/10.1002/2014GC005419/abstract

Zero-temperature phase of the XY spin glass in two dimensions: Genetic embedded matching heuristic

For many real spin-glass materials, the Edwards-Anderson model with continuous-symmetry spins is more realistic than the rather better understood Ising variant. In principle, the nature of an occurring spin-glass phase in such systems might be inferred from an analysis of the zero-temperature properties. Unfortunately, with few exceptions, the problem of finding ground-state configurations is a non-polynomial problem computationally, such that efficient approximation algorithms are called for. Here, we employ the recently developed genetic embedded matching (GEM) heuristic to investigate the nature of the zero-temperature phase of the bimodal XY spin glass in two dimensions. We analyze bulk properties such as the asymptotic ground-state energy and the phase diagram of disorder strength vs. disorder concentration. For the case of a symmetric distribution of ferromagnetic and antiferromagnetic bonds, we find that the ground state of the model is unique up to a global O(2) rotation of the spins. In particular, there are no extensive degeneracies in this model. The main focus of this work is on an investigation of the excitation spectrum as probed by changing the boundary conditions. Using appropriate finite-size scaling techniques, we consistently determine the stiffness of spin and chiral domain walls and the corresponding fractal dimensions. Most noteworthy, we find that the spin and chiral channels are characterized by two distinct stiffness exponents and, consequently, the system displays spin-chirality decoupling at large length scales. Results for the overlap distribution do not support the possibility of a multitude of thermodynamic pure states.Comment: 18 pages, RevTex 4, moderately revised version as publishe

Fifteen Years of Chandra Operation: Scientific Highlights and Lessons Learned

NASA's Chandra X-Ray Observatory, designed for three years of operation with a goal of five years is now entering its 15-th year of operation. Thanks to its superb angular resolution, the Observatory continues to yield new and exciting results, many of which were totally unanticipated prior to launch. We discuss the current technical status, review recent scientific highlights, indicate a few future directions, and present what we feel is the most important lesson learned from our experience of building and operating this great observatory

Genetic embedded matching approach to ground states in continuous-spin systems

Due to an extremely rugged structure of the free energy landscape, the determination of spin-glass ground states is among the hardest known optimization problems, found to be NP-hard in the most general case. Owing to the specific structure of local (free) energy minima, general-purpose optimization strategies perform relatively poorly on these problems, and a number of specially tailored optimization techniques have been developed in particular for the Ising spin glass and similar discrete systems. Here, an efficient optimization heuristic for the much less discussed case of continuous spins is introduced, based on the combination of an embedding of Ising spins into the continuous rotators and an appropriate variant of a genetic algorithm. Statistical techniques for insuring high reliability in finding (numerically) exact ground states are discussed, and the method is benchmarked against the simulated annealing approach.Comment: 17 pages, 12 figures, 1 tabl