Extraction efficiency of drifting electrons in a two-phase xenon time projection chamber

We present a measurement of the extraction efficiency of quasi-free electrons from the liquid into the gas phase in a two-phase xenon time-projection chamber. The measurements span a range of electric fields from 2.4 to 7.1 kV/cm in the liquid xenon, corresponding to 4.5 to 13.1 kV/cm in the gaseous xenon. Extraction efficiency continues to increase at the highest extraction fields, implying that additional charge signal may be attained in two-phase xenon detectors through careful high-voltage engineering of the gate-anode region

Multilingual education in South Africa: the role of publishers

The South African constitution and related legislative tools provide a supportive framework for multilingual education. Successful implementation, however, requires appropriate learning materials and questions remain as to the vision and commitment of publishers to producing them. Based on an analysis of currently available books for children and interviews with publishers and key figures in the book value chain, this paper explores both the educational rationale for African language publishing and the issues that constrain expansion. These issues include the heavy dependence on the schools market in a society where the majority of the population cannot or do not buy books, the consequences of the slow implementation of the government language-in-education policy, and the particular challenges faced by small publishers. It argues that in order to move beyond dependence on the schools market, publishers need to look critically at the content of the materials they are producing, methods of reaching the huge, untapped markets, and pricing strategies. It also considers differing opinions about the usefulness of translation in increasing the amount of reading material in African languages. Finally, it concludes that responsibility for finding a way out of the current impasse lies with both government and the publishing industry

Calibration of a two-phase xenon time projection chamber with a 37^{37}Ar source

We calibrate a two-phase xenon detector at 0.27 keV in the charge channel and at 2.8 keV in both the light and charge channels using a $^{37}$Ar source that is directly released into the detector. We map the light and charge yields as a function of electric drift field. For the 2.8 keV peak, we calculate the Thomas-Imel box parameter for recombination and determine its dependence on drift field. For the same peak, we achieve an energy resolution, $E_{\sigma}/E_{mean}$, between 9.8% and 10.8% for 0.1 kV/cm to 2 kV/cm electric drift fields.Comment: 12 pages, 7 figure

Hydrodynamic instabilities in gaseous detonations: comparison of Euler, Navier–Stokes, and large-eddy simulation

A large-eddy simulation is conducted to investigate the transient structure of an unstable detonation wave in two dimensions and the evolution of intrinsic hydrodynamic instabilities. The dependency of the detonation structure on the grid resolution is investigated, and the structures obtained by large-eddy simulation are compared with the predictions from solving the Euler and Navier–Stokes equations directly. The results indicate that to predict irregular detonation structures in agreement with experimental observations the vorticity generation and dissipation in small scale structures should be taken into account. Thus, large-eddy simulation with high grid resolution is required. In a low grid resolution scenario, in which numerical diffusion dominates, the structures obtained by solving the Euler or Navier–Stokes equations and large-eddy simulation are qualitatively similar. When high grid resolution is employed, the detonation structures obtained by solving the Euler or Navier–Stokes equations directly are roughly similar yet equally in disagreement with the experimental results. For high grid resolution, only the large-eddy simulation predicts detonation substructures correctly, a fact that is attributed to the increased dissipation provided by the subgrid scale model. Specific to the investigated configuration, major differences are observed in the occurrence of unreacted gas pockets in the high-resolution Euler and Navier–Stokes computations, which appear to be fully combusted when large-eddy simulation is employed

Lepton flavor violation at linear collider experiments in supersymmetric grand unified theories

Lepton flavor violation at linear collider experiments is discussed. We show that detectable lepton flavor violation could occur through scalar lepton pair production and decay in the supersymmetric SU(5) grand unified theory in spite of the stringent present experimental constraints by rare process searches. Possible cross sections about 40fb for an e+e- collider and 280fb for an e-e- collider are illustrated.Comment: 12 pages, including 3 figures, REVTeX, eps

Manifestation of the Nuclear Anapole Moment in M1 Transitions in Thallium

We calculate nuclear spin-dependent parity non-conserving $E1$-amplitudes for optical transition $6p_{1/2,F} -> 6p_{3/2,F'}$ and for hyperfine transition $6p_{1/2,F} -> 6p_{1/2,F'}$ in Tl. Experimental limit on the former amplitude placed by Vetter et al. [PRL, 74, 2658 (1995)] corresponds to the anapole moment constant $\kappa_a = -0.26 \pm 0.27$. Experiment on the hyperfine transition can give direct measurement of the spin-dependent amplitude, because spin-independent amplitude turns to zero.Comment: 4 pages, LaTeX2e, uses revtex4.cl

The development of student learning and information literacy: a case study [conference item]

Literacy is documented as a fundamental human right. The ability to exercise this right improves an individual’s life chances by achieving their personal, social, occupational and educational goals, and it opens opportunities for social, economic and political integration. Currently in an information and knowledge society, there is a salient need for Information Literacy (IL). IL can be defined as knowing when and why one might need information, where to find it, and how to evaluate, use and communicate it in an ethical manner. There is a need for undergraduate and postgraduate students to demonstrate a competency with information literacy skills. For example it is essential for the student to develop a thesis statement, i.e. research question and to consequently search, organise, share and evaluate the results. In this paper we present a case studyhighligting the role of Library and Student Support (LSS) based at Middlesex University London. LSS works in conjunction with University Departments (Schools) and leads on the development and implementation of a coherent and strategic approach to the development of learner competencies. These are identified through the development and implementation of relevant University policies and strategies. We argue that other Higher Education institutions may benefit from our experience of implementing IL policy in collaboration with a Library and Student Support Service

Management of incidentally detected heart murmurs in dogs and cats

A dog or a cat has an incidentally detected heart murmur if the murmur is an unexpected discovery during a veterinary consultation that was not initially focused on the cardiovascular system. This document presents approaches for managing dogs and cats that have incidentally-detected heart murmurs, with an emphasis on murmur characteristics, signalment profiling, and multifactorial decision-making to choose an optimal course for a given patient

A Gapless Theory of Bose-Einstein Condensation in Dilute Gases at Finite Temperature

In this paper we develop a gapless theory of BEC which can be applied to both trapped and homogeneous gases at zero and finite temperature. The many-body Hamiltonian for the system is written in a form which is approximately quadratic with higher order cubic and quartic terms. The quadratic part is diagonalized exactly by transforming to a quasiparticle basis, while the non-quadratic terms are dealt with using first and second order perturbation theory. The conventional treatment of these terms, based on factorization approximations, is shown to be inconsistent. Infra-red divergences can appear in individual terms of the perturbation expansion, but we show analytically that the total contribution beyond quadratic order is finite. The resulting excitation spectrum is gapless and the energy shifts are small for a dilute gas away from the critical region, justifying the use of perturbation theory. Ultra-violet divergences can appear if a contact potential is used to describe particle interactions. We show that the use of this potential as an approximation to the two-body T-matrix leads naturally to a high-energy renormalization. The theory developed in this paper is therefore well-defined at both low and high energy and provides a systematic description of Bose-Einstein condensation in dilute gases. It can therefore be used to calculate the energies and decay rates of the excitations of the system at temperatures approaching the phase transition.Comment: 39 pages of Revtex. 1 figur