New chemical analyses of the Suurberg volcanic rocks and their significance in relation to Mesozoic volcanism in Southern Africa

Volcanic rocks are found associated with several of the late Mesozoic basins of southern South Africa. Bentonites are known from Plettenberg Bay and, according to an unconfirmed report, they are also found in the Worcester Basin, while vitric tuffs have been recorded from east of Oudtshoorn. The most extensive occurrences, however, are those of the Suurberg Group, which crops out sporadically around the margins of the Algoa Basin

An Aerothermoelastic Analysis Framework Enhanced by Model Order Reduction With Applications

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143034/1/6.2017-1601.pd

Quantum Relativity of Subsystems

One of the most basic notions in physics is the partitioning of a system into subsystems, and the study of correlations among its parts. In this work, we explore these notions in the context of quantum reference frame (QRF) covariance, in which this partitioning is subject to a symmetry constraint. We demonstrate that different reference frame perspectives induce different sets of subsystem observable algebras, which leads to a gauge-invariant, frame-dependent notion of subsystems and entanglement. We further demonstrate that subalgebras which commute before imposing the symmetry constraint can translate into non-commuting algebras in a given QRF perspective after symmetry imposition. Such a QRF perspective does not inherit the distinction between subsystems in terms of the corresponding tensor factorizability of the kinematical Hilbert space and observable algebra. Since the condition for this to occur is contingent on the choice of QRF, the notion of subsystem locality is frame-dependent.Comment: 8+9 pages, 1 figur

High resolution Compton scattering as a Probe of the Fermi surface in the Iron-based superconductor LaO1−xFxFeAsLaO_{1-x}F_xFeAs

We have carried out first principles all-electron calculations of the (001)-projected 2D electron momentum density and the directional Compton profiles along the [100], [001] and [110] directions in the Fe-based superconductor LaOFeAs within the framework of the local density approximation. We identify Fermi surface features in the 2D electron momentum density and the directional Compton profiles, and discuss issues related to the observation of these features via Compton scattering experiments.Comment: 4 pages, 3 figure

Displays and claims of understanding in conversation by people with aphasia

Background: There is scope for additional research into the specific linguistic and sequential structures used in speech and language therapist (SLT)-led therapeutic conversations with people with aphasia (PWA). Whilst there is some evidence that SLTs use different conversational strategies than the partners of PWA, research to date has focussed mainly on measuring the effects of conversation-based therapies—not on analysing therapeutic conversations taking place between SLTs and PWA. Aims: This paper presents an analysis of the use of oh-prefacing by some PWA during therapeutic supported conversations with SLTs. Methods & Procedures: Normally occurring therapeutic conversations between SLTs and PWA after stroke were qualitatively analysed using Conversation Analysis. Interactions with five PWA were video-recorded, involving three different specialist stroke SLTs. Outcomes & Results: The analysis revealed a difference in the way some PWA use turns that display understanding (e.g., oh right) versus those that continue the conversation, merely claiming understanding (e.g., right). This use of oh-prefacing is similar to that described in the literature on typical conversations. In our data, SLTs are shown to treat oh-prefaced turns differently from non-oh-prefaced turns, by pursuing the topic in the latter, and progressing on to a new topic in the former. Conclusions: At least some PWA use oh-prefacing in the same way as non-language-impaired adults to display understanding of information versus merely claiming to understand. The SLTs in our data are shown to treat non-oh-prefaced turns as mere claims of understanding by providing the PWA with additional information, using supported conversation techniques, and pursuing additional same-topic talk, whereas oh-prefaced turns are treated as displays of understanding by being confirmed, and leading to changes of topic. This study is a first step in providing SLTs with a clearer understanding of the ways in which they are assessing the understanding of PWA, which may in turn help them better support non-therapy staff

A case study of boundary layer ventilation by convection and coastal processes

It is often assumed that ventilation of the atmospheric boundary layer is weak in the absence of fronts, but is this always true? In this paper we investigate the processes responsible for ventilation of the atmospheric boundary layer during a nonfrontal day that occurred on 9 May 2005 using the UK Met Office Unified Model. Pollution sources are represented by the constant emission of a passive tracer everywhere over land. The ventilation processes observed include shallow convection, turbulent mixing followed by large-scale ascent, a sea breeze circulation and coastal outflow. Vertical distributions of tracer are validated qualitatively with AMPEP (Aircraft Measurement of chemical Processing Export fluxes of Pollutants over the UK) CO aircraft measurements and are shown to agree impressively well. Budget calculations of tracers are performed in order to determine the relative importance of these ventilation processes. Coastal outflow and the sea breeze circulation were found to ventilate 26% of the boundary layer tracer by sunset of which 2% was above 2 km. A combination of coastal outflow, the sea breeze circulation, turbulent mixing and large-scale ascent ventilated 46% of the boundary layer tracer, of which 10% was above 2 km. Finally, coastal outflow, the sea breeze circulation, turbulent mixing, large-scale ascent and shallow convection together ventilated 52% of the tracer into the free troposphere, of which 26% was above 2 km. Hence this study shows that significant ventilation of the boundary layer can occur in the absence of fronts (and thus during high-pressure events). Turbulent mixing and convection processes can double the amount of pollution ventilated from the boundary layer

Equivalence of Approaches to Relational Quantum Dynamics in Relativistic Settings

We have previously shown that three approaches to relational quantum dynamics—relational Dirac observables, the Page-Wootters formalism and quantum deparametrizations—are equivalent. Here we show that this “trinity” of relational quantum dynamics holds in relativistic settings per frequency superselection sector. Time according to a clock subsystem is defined via a positive operator-valued measure (POVM) that is covariant with respect to the group generated by its (quadratic) Hamiltonian. This differs from the usual choice of a self-adjoint clock observable conjugate to the clock momentum. It also resolves Kuchař\u27s criticism that the Page-Wootters formalism yields incorrect localization probabilities for the relativistic particle when conditioning on a Minkowski time operator. We show that conditioning instead on the covariant clock POVM results in a Newton-Wigner type localization probability commonly used in relativistic quantum mechanics. By establishing the equivalence mentioned above, we also assign a consistent conditional-probability interpretation to relational observables and deparametrizations. Finally, we expand a recent method of changing temporal reference frames, and show how to transform states and observables frequency-sector-wise. We use this method to discuss an indirect clock self-reference effect and explore the state and temporal frame-dependence of the task of comparing and synchronizing different quantum clocks