Teacher and child talk in active learning and whole-class contexts : some implications for children from economically less advantaged home backgrounds

This paper reports the experiences of 150 children and six primary teachers when active learning pedagogies were introduced into the first year of primary schools. Although active learning increased the amount of talk between children, those from socio-economically advantaged homes talked more than those from less advantaged homes. Also, individual children experienced very little time engaged in high-quality talk with the teacher, despite the teachers spending over one-third of their time responding to children's needs and interests. Contextual differences, such as the different staffing ratios in schools and pre-schools,may affect how well the benefits of active learning transfer from preschool contexts into primary schools. Policy-makers and teachers should pay particular attention to the implications of this for the education of children from economically less advantaged home backgrounds

The Search for Celestial Positronium via the Recombination Spectrum

Positronium is the short-lived atom consisting of a bound electron-positron pair. In the triplet state, when the spins of both particles are parallel, radiative recombination lines will be emitted prior to annihilation. The existence of celestial positronium is revealed through gamma-ray observations of its annihilation products. These observations however have intrinsically low angular resolution. In this paper we examine the prospects for detecting the positronium recombination spectrum. Such observations have the potential to reveal discrete sources of positrons for the first time and will allow the acuity of optical telescopes and instrumentation to be applied to observations of high energy phenomena. We review the theory of the positronium recombination spectrum and provide formulae to calculate expected line strengths from the positrons production rate and for different conditions in the interstellar medium. We estimate the positronium emission line strengths for several classes of Galactic and extragalactic sources. These are compared to current observational limits and to current and future sensitivities of optical and infrared instrumentation. We find that observations of the Ps-alpha line should soon be possible due to recent advances in near-infrared spectroscopy.Comment: Accepted for publication in Ap

Literature circles, gender and reading for enjoyment

The research was commissioned through Information and Analytical Services Division, which is responsible for providing analytical services within the Scottish Executive Education Department (SEED). Their work is part of a multidisciplinary unit (consisting of researchers, economists and statistics staff) and the staff undertakes and funds economic analysis and social research in the fields of: school education; children, young people and social work: architecture; and tourism, culture and sport

Electroweak Precision Data and Gravitino Dark Matter

Electroweak precision measurements can provide indirect information about the possible scale of supersymmetry already at the present level of accuracy. We review present day sensitivities of precision data in mSUGRA-type models with the gravitino as the lightest supersymmetric particle (LSP). The chi^2 fit is based on M_W, sin^2 theta_eff, (g-2)_mu, BR(b -> s gamma) and the lightest MSSM Higgs boson mass, M_h. We find indications for relatively light soft supersymmetry-breaking masses, offering good prospects for the LHC and the ILC, and in some cases also for the Tevatron.Comment: 4 pages, 1 figure. Talk given at the LCWS06 March 2006, Bangalore, India. References adde

Virtual RTCP: A Case Study of Monitoring and Repair for UDP-based IPTV Systems

IPTV systems have seen widespread deployment, but often lack robust mechanisms for monitoring the quality of experience. This makes it difficult for network operators to ensure that their services match the quality of traditional broadcast TV systems, leading to consumer dissatisfaction. We present a case study of virtual RTCP, a new framework for reception quality monitoring and reporting for UDP-encapsulated MPEG video delivered over IP multicast. We show that this allows incremental deployment of reporting infrastructure, coupled with effective retransmission-based packet loss repair

CP-Violating MSSM Higgs Bosons in the Light of LEP 2

In the MSSM, the CP parities of the neutral Higgs bosons may be mixed by radiative effects induced by explicit CP violation in the third generation of squarks. To allow for this possibility, we argue that the charged Higgs-boson mass and tan(beta) should be used to parametrize the MSSM Higgs sector. We introduce a new benchmark scenario of maximal CP violation appropriate for direct searches of CP-violating MSSM Higgs bosons. We show that the bounds established by LEP 2 on the MSSM Higgs sector may be substantially relaxed at low and intermediate values of tan(beta) in the presence of CP violation, and comment on possible Higgs boson signatures at LEP 2 within this framework.Comment: 16 pages, LaTeX, 4 encapsulated figure

Diffractive jet production in a simple model with applications to HERA

In diffractive jet production, two high energy hadrons A and B collide and produce high transverse momentum jets, while hadron A is diffractively scattered. Ingelman and Schlein predicted this phenomenon. In their model, part of the longitudinal momentum transferred from hadron A is delivered to the jet system, part is lost. Lossless diffractive jet production, in which all of this longitudinal momentum is delivered to the jet system, has been discussed by Collins, Frankfurt, and Strikman. We study the structure of lossless diffractive jet production in a simple model. The model suggests that the phenomenon can be probed experimentally at HERA, with A being a proton and B being a bremsstrahlung photon with virtuality $Q^2$. Lossless events should be present for small $Q^2$, but not for $Q^2$ larger than $1/R_{\rm P}^2$, where $R_{\rm P}$ is a characteristic size of the pomeron.Comment: 23 pages, REVTeX 3.0 with 8 postscript figures compressed with uufiles, OITS 536 and AZPH-TH/94-0

Neutrino Masses, Mixing Angles and the Unification of Couplings in the MSSM

In the light of the gathering evidence for $\nu_{\mu}-\nu_{\tau}$ neutrino oscillations, coming in particular from the Super-Kamiokande data on atmospheric neutrinos, we re-analyze the unification of gauge and Yukawa couplings within the minimal supersymmetric extension of the Standard Model (MSSM). Guided by a range of different grand-unified models, we stress the relevance of large mixing in the lepton sector for the question of bottom-tau Yukawa coupling unification. We also discuss the dependence of the favoured value of $\tan\beta$ on the characteristics of the high-energy quark and lepton mass matrices. In particular, we find that, in the presence of large lepton mixing, Yukawa unification can be achieved for intermediate values of $\tan\beta$ that were previously disfavoured. The renormalization-group sensitivity to the structures of different mass matrices may enable Yukawa unification to serve as a useful probe of GUT models.Comment: 29 pages, latex, 5 figure