Making connections: Integrative theological education in Africa

Naidoo, M. (ed.), (Stellenbosch: SUNPRess, 2021). xiv+180 pages. ISBN 978-1-991201-46-1

Spectral Density on the Lattice

Spectral density in the pseudoscalar and vector channels is extracted from the SU(2) lattice quenched data. It is shown to consist of three sharp poles within the energy range accessible on the lattice.Comment: 38 pages, uuencoded tar-compressed ps-fil

Expansion Aspect of Color Transparency on the Lattice

The opportunity to observe color transparency (CT) is determined by how rapidly a small-sized hadronic wave packet expands. Here we use SU(2) lattice gauge theory with Wilson fermions in the quenched approximation to investigate the expansion. The wave packet is modeled by a point hadronic source, often used as an interpolating field in lattice calculations. The procedure is to determine the Euclidean time (t), pion channel, Bethe-Salpeter amplitude $\Psi(r,t)$, and then evaluate $b^2(t)=\int d^3 r \Psi(r,t) r^2 sin^2 \theta \Psi_{\pi}(r)$. This quantity represents the soft interaction of a small-sized wave packet with a pion. The time dependence of $b^2(t)$ is fit as a superposition of three states, which is found sufficient to reproduce a reduced size wave packet. Using this superposition allows us to make the analytic continuation required to study the wave packet expansion in real time. We find that the matrix elements of the soft interaction $\hat b^2$ between the excited and ground state decrease rapidly with the energy of the excited state.Comment: 19 pages, latex, 4 figure

Talk the talk, walk the walk: Defining Critical Race Theory in research

Over the last decade there has been a noticeable growth in published works citing Critical Race Theory (CRT). This has led to a growth in interest in the UK of practical research projects utilising CRT as their framework. It is clear that research on 'race' is an emerging topic of study. What is less visible is a debate on how CRT is positioned in relation to methodic practice, substantive theory and epistemological underpinnings. The efficacy of categories of data gathering tools, both traditional and non-traditional is a discussion point here to explore the complexities underpinning decisions to advocate a CRT framework. Notwithstanding intersectional issues, a CRT methodology is recognisable by how philosophical, political and ethical questions are established and maintained in relation to racialised problematics. This paper examines these tensions in establishing CRT methodologies and explores some of the essential criteria for researchers to consider in utilising a CRT framework. © 2012 Copyright Taylor and Francis Group, LLC

Magnetic Field Generation in Stars

Enormous progress has been made on observing stellar magnetism in stars from the main sequence through to compact objects. Recent data have thrown into sharper relief the vexed question of the origin of stellar magnetic fields, which remains one of the main unanswered questions in astrophysics. In this chapter we review recent work in this area of research. In particular, we look at the fossil field hypothesis which links magnetism in compact stars to magnetism in main sequence and pre-main sequence stars and we consider why its feasibility has now been questioned particularly in the context of highly magnetic white dwarfs. We also review the fossil versus dynamo debate in the context of neutron stars and the roles played by key physical processes such as buoyancy, helicity, and superfluid turbulence,in the generation and stability of neutron star fields. Independent information on the internal magnetic field of neutron stars will come from future gravitational wave detections. Thus we maybe at the dawn of a new era of exciting discoveries in compact star magnetism driven by the opening of a new, non-electromagnetic observational window. We also review recent advances in the theory and computation of magnetohydrodynamic turbulence as it applies to stellar magnetism and dynamo theory. These advances offer insight into the action of stellar dynamos as well as processes whichcontrol the diffusive magnetic flux transport in stars.Comment: 41 pages, 7 figures. Invited review chapter on on magnetic field generation in stars to appear in Space Science Reviews, Springe

Controlling roughening processes in the stochastic Kuramoto–Sivashinsky equation

We present a novel control methodology to control the roughening processes of semilinear parabolic stochastic partial differential equations in one dimension, which we exemplify with the stochastic Kuramoto-Sivashinsky equation. The original equation is split into a linear stochastic and a nonlinear deterministic equation so that we can apply linear feedback control methods. Our control strategy is then based on two steps: first, stabilize the zero solution of the deterministic part and, second, control the roughness of the stochastic linear equation. We consider both periodic controls and point actuated ones, observing in all cases that the second moment of the solution evolves in time according to a power-law until it saturates at the desired controlled value

Magnetic fields in supernova remnants and pulsar-wind nebulae

We review the observations of supernova remnants (SNRs) and pulsar-wind nebulae (PWNe) that give information on the strength and orientation of magnetic fields. Radio polarimetry gives the degree of order of magnetic fields, and the orientation of the ordered component. Many young shell supernova remnants show evidence for synchrotron X-ray emission. The spatial analysis of this emission suggests that magnetic fields are amplified by one to two orders of magnitude in strong shocks. Detection of several remnants in TeV gamma rays implies a lower limit on the magnetic-field strength (or a measurement, if the emission process is inverse-Compton upscattering of cosmic microwave background photons). Upper limits to GeV emission similarly provide lower limits on magnetic-field strengths. In the historical shell remnants, lower limits on B range from 25 to 1000 microGauss. Two remnants show variability of synchrotron X-ray emission with a timescale of years. If this timescale is the electron-acceleration or radiative loss timescale, magnetic fields of order 1 mG are also implied. In pulsar-wind nebulae, equipartition arguments and dynamical modeling can be used to infer magnetic-field strengths anywhere from about 5 microGauss to 1 mG. Polarized fractions are considerably higher than in SNRs, ranging to 50 or 60% in some cases; magnetic-field geometries often suggest a toroidal structure around the pulsar, but this is not universal. Viewing-angle effects undoubtedly play a role. MHD models of radio emission in shell SNRs show that different orientations of upstream magnetic field, and different assumptions about electron acceleration, predict different radio morphology. In the remnant of SN 1006, such comparisons imply a magnetic-field orientation connecting the bright limbs, with a non-negligible gradient of its strength across the remnant.Comment: 20 pages, 24 figures; to be published in SpSciRev. Minor wording change in Abstrac

Higher Resonance Contamination of pi NN Couplings Obtained Via the Three-Point Function Method in QCD Sum Rules

We investigate the size of potential higher pseudoscalar resonance contaminations of the estimates of isospin-conserving and isospin-violating $\pi NN$ couplings obtained using the 3-point function method in QCD sum rules. For the isospin-conserving case it is shown that conventional models of the isovector pseudoscalar spectral function imply resonance decay constants large enough to create significant contaminations, and that assuming these models are incorrect, and that the decay constants are actually much smaller, implies physically implausible values for the flavor-breaking quark condensate ratios. For the isospin-violating case it is shown explicitly that such resonance contamination is unavoidably present and precludes using the 3-point function method as a means of estimating the at present unmeasured isospin-violating $\pi NN$ couplings.Comment: 8 page

An Adeno-Associated Viral Vector Capable of Penetrating the Mucus Barrier to Inhaled Gene Therapy

Diffusion of the viral vectors evaluated in inhaled gene therapy clinical trials to date are largely hindered within airway mucus, which limits their access to, and transduction of, the underlying airway epithelium prior to clearance from the lung. Here, we discovered that adeno-associated virus (AAV) serotype 6 was able to rapidly diffuse through mucus collected from cystic fibrosis (CF) patients, unlike previously tested AAV serotypes. A point mutation of the AAV6 capsid suggests a potential mechanism by which AAV6 avoids adhesion to the mucus mesh. Significantly greater transgene expression was achieved with AAV6 compared to a mucoadhesive serotype, AAV1, in air-liquid interface cultures of human CF bronchial epithelium with naturally secreted mucus or induced mucus hypersecretion. In addition, AAV6 achieved superior distribution and overall level of transgene expression compared to AAV1 in the airways and whole lungs, respectively, of transgenic mice with airway mucus obstruction. Our findings motivate further evaluation and clinical development of AAV6 for inhaled gene therapy