Resolving Exceptional Configurations

In lattice QCD with Wilson fermions, exceptional configurations arise in the quenched approximation at small quark mass. The origin of these large previously uncontrolled lattice artifacts is identified. A simple well-defined procedure (MQA) is presented which removes the artifacts while preserving the correct continuum limit.Comment: Talk presented by E. Eichten at Lattice 97, Edinburgh(UK), July97. 6 pages, LaTeX, 1 table, 5 figure

Exploring parental and driver knowledge, use and beliefs of child restraints such as infant car seats, toddler seats and booster seats in South Africa

Abstract: The purpose of this paper is to determine parents’ and drivers’ knowledge, use and beliefs of child restraints amongst lower middle-class groups in South Africa. The study was qualitative in nature, and data was collected from parents or drivers of children aged birth - 11 with a motor vehicle in Gauteng. Through the application of the convenience sampling technique, a total of 14 parents and drivers with children at selected pre-schools and primary schools, who are in the lower middleclass groups and who reside in the cities of Johannesburg, Tshwane and Ekurhuleni, were selected. The Morse and Field Approach was used to analyse the data because the steps of this data analysis method are clear, easy to follow and comprehensible. There is a lack of knowledge and usage of child restraints among lower middle-class parents and drivers within Gauteng. The results also indicate that there are variables that are predictive of age-appropriate restraint use and knowledge, and that parents hold specific beliefs around child restraints. Lastly, the results indicated that the parents and drivers have rarely seen any advertisements on child restraints in South Africa. By exploring the topic of usage, knowledge, beliefs and the social marketing of child restraints, strategies have been identified on how to overcome the major challenge of child injuries in motor vehicle accidents in South Africa. This study promotes child restraint usage on South African roads and assists organisations in South Africa to better understand that social marketing is necessary to change the behaviour of parents with regard to child restraints usage

First Principles Calculation of Anomalous Hall Conductivity in Ferromagnetic bcc Fe

We perform a first principles calculation of the anomalous Hall effect in ferromagnetic bcc Fe. Our theory identifies an intrinsic contribution to the anomalous Hall conductivity and relates it to the k-space Berry phase of occupied Bloch states. The theory is able to account for both dc and magneto-optical Hall conductivities with no adjustable parameters.Comment: 4 pages, 6 figures, author list correcte

Spin Disorder and Magnetic Anisotropy in Fe3O4 Nanoparticles

We have studied the magnetic behavior of dextran-coated magnetite (Fe$_3$O$_4$) nanoparticles with median particle size \left=8 $nm$. Magnetization curves and in-field M\"ossbauer spectroscopy measurements showed that the magnetic moment $M_S$ of the particles was much smaller than the bulk material. However, we found no evidence of magnetic irreversibility or non-saturating behavior at high fields, usually associated to spin canting. The values of magnetic anisotropy $K_{eff}$ from different techniques indicate that surface or shape contributions are negligible. It is proposed that these particles have bulk-like ferrimagnetic structure with ordered A and B sublattices, but nearly compensated magnetic moments. The dependence of the blocking temperature with frequency and applied fields, $T_B(H,\omega)$, suggests that the observed non-monotonic behavior is governed by the strength of interparticle interactions.Comment: 11 pages, 7 figures, 3 Table

Lattice Gauge Theories and the Heisenberg Antiferromagnetic Chain

We study the strongly coupled 2-flavor lattice Schwinger model and the SU(2)-color QCD_2. The strong coupling limit, even with its inherent nonuniversality, makes accurate predictions of the spectrum of the continuum models and provides an intuitive picture of the gauge theory vacuum. The massive excitations of the gauge model are computable in terms of spin-spin correlators of the quantum Heisenberg antiferromagnetic spin-1/2 chain.Comment: Proceedings LATTICE99 (spin models), 3 page