The electronic structure of the Nax_xCoO2_2 surface

The idea that surface effects may play an important role in suppressing $e_g'$ Fermi surface pockets on Na$_x$CoO$_2$ $(0.333 \le x \le 0.75)$ has been frequently proposed to explain the discrepancy between LDA calculations (performed on the bulk compound) which find $e_g$' hole pockets present and ARPES experiments, which do not observe the hole pockets. Since ARPES is a surface sensitive technique it is important to investigate the effects that surface formation will have on the electronic structure of Na$_{1/3}$CoO$_2$ in order to more accurately compare theory and experiment. We have calculated the band structure and Fermi surface of cleaved Na$_{1/3}$CoO$_2$ and determined that the surface non-trivially affects the fermiology in comparison to the bulk. Additionally, we examine the likelihood of possible hydroxyl cotamination and surface termination. Our results show that a combination of surface formation and contamination effects could resolve the ongoing controversy between ARPES experiments and theory.Comment: 4 pages, 2 figure

The origin of a1g_{1g} and eg_g' orderings in Nax_xCoO2_2

It has often been suggested that correlation effects suppress the small e_g' Fermi surface pockets of NaxCoO_2 that are predicted by LDA, but absent in ARPES measurements. It appears that within the dynamical mean field theory (DMFT) the ARPES can be reproduced only if the on-site energy of the eg' complex is lower than that of the a1g complex at the one-electron level, prior to the addition of local correlation effects. Current estimates regarding the order of the two orbital complexes range from -200 meV to 315 meV in therms of the energy difference. In this work, we perform density functional theory calculations of this one-electron splitting \Delta= \epsilon_a1g-\epsilon_e_g' for the full two-layer compound, Na2xCo2O4, accounting for the effects of Na ordering, interplanar interactions and octahedral distortion. We find that \epsilon a_1g-\epsilon e_g' is negative for all Na fillings and that this is primarily due to the strongly positive Coulomb field created by Na+ ions in the intercalant plane. This field disproportionately affects the a_1g orbital which protrudes farther upward from the Co plane than the e_g' orbitals. We discuss also the secondary effects of octahedral compression and multi-orbital filling on the value of \Delta as a function of Na content. Our results indicate that if the e_g' pockets are indeed suppressed that can only be due to nonlocal correlation effects beyond the standard DMFT.Comment: 4 pages, 3 figure

Supply chain constraints in the South African construction industry – perspectives from supply chain practitioners

Abstract : In the face of slowing economies globally, the construction industry faces many challenges such as socio-economic stress, resource shortages, institutional weaknesses and a general inability to respond to key issues. These have intensified and become more severe in recent years. Empirical research in supply chain management points to barriers that limit construction industries in developing countries such as South Africa. This paper aims to explore supply chain constraints in the South African construction industry. Relevant literature was reviewed and insights from 15 experienced supply chain practitioners were elicited by means of semi-structured interviews. Content analysis was employed using the ATLAS.ti (version 7) software to analyse qualitative data. Six themes emerged from the interviews, which include lack of investment in supply chains, lack of supply chain innovation process constraints, supply chain change management, supply chain collaboration, supply chain leadership, and time management. It is recommended that construction companies adopt supply chain management systems, integrated solutions, and collaborative project management tools and technologies

Exploring clinician attitudes to addiction recovery in Victoria, Australia

Internationally, the alcohol and other drug (AOD) field has an increasing focus on recovery-oriented care, however there has been little research addressing the impacts in Australia. This study explores the attitudes of AOD clinicians toward recovery-oriented care in Victoria. Data was collected from 50 AOD clinicians and managers across six AOD services. Data collection included completion of a structured questionnaire addressing recovery attitudes and beliefs and semistructured group interviews. Although participants agreed with the broad concept of recovery, there was disagreement over the appropriateness of recovery as a term. The findings support that the development of a set of guiding recovery principles would be more useful than a simple definition

Connected OFCity Challenge: Addressing the Digital Divide in the Developing World

Over the past 50 years, the development of information and communications technology has provided unprecedented support to the steady economic growth of developed countries. In recent years, some of the largest growth has been reported in emerging economies, which, however, often lack adequate telecommunications infrastructure to further sustain their development. Although a number of service providers and system vendors have started to address the issue, the challenges they encounter are substantially different from those in the developed world, including an unreliable electricity grid, poor fiber infrastructure, low revenue expectations, and often a harsh climate environment. This paper reports use cases and solutions pertinent to the development of the networking infrastructure in emerging economies, provided by organizations directly involved in such activities. After providing some background information on the current state of network infrastructure and the main challenges for Africa and rural China, the paper provides details on two proposed solutions. The first focuses on the provisioning of services and network infrastructure through the development of low-cost data centers, whereas the second proposes cost-effective adaptation of both fiber and hybrid copper-fiber technology to rural areas. The article is concluded with a brief discussion on the complementarity of the two approaches

A Multi-Class SWAP-Test Classifier

Multi-class classification problems are fundamental in many varied domains in research and industry. To solve multi-class classification problems, heuristic strategies such as One-vs-One or One-vs-All can be employed. However, these strategies require the number of binary classification models developed to grow with the number of classes. Recent work in quantum machine learning has seen the development of multi-class quantum classifiers that circumvent this growth by learning a mapping between the data and a set of label states. This work presents the first multi-class SWAP-Test classifier inspired by its binary predecessor and the use of label states in recent work. With this classifier, the cost of developing multiple models is avoided. In contrast to previous work, the number of qubits required, the measurement strategy, and the topology of the circuits used is invariant to the number of classes. In addition, unlike other architectures for multi-class quantum classifiers, the state reconstruction of a single qubit yields sufficient information for multi-class classification tasks. Both analytical results and numerical simulations show that this classifier is not only effective when applied to diverse classification problems but also robust to certain conditions of noise.Comment: 13 pages, 9 figure

Cerebral Palsy and Criteria Implicating Intrapartum Hypoxia in Neonatal Encephalopathy – An Obstetric Perspective for the South African Setting

The science surrounding cerebral palsy indicates  that it is a complex medical condition with multiple contributing variables and factors, and causal pathways are often extremely difficult to delineate. The pathophysiological processes are often juxtaposed on antenatal factors, genetics, toxins, fetal priming, failure of neuroscientific autoregulatory mechanisms, abnormal biochemistry and abnormal metabolic pathways. Placing this primed compromised compensated brain through the stresses of an intrapartum process could be the final straw in the pathway  to brain injury and later CP.  It is thus simplistic to base causation of cerebral palsy on only an intrapartum perspective with radiological ‘confirmation’, as is often the practice in medicolegal cases in South African courts. The present modalities (MRI and CTG when available) that retrospectively attempt to determine causation in courts are inadequate when used in isolation. Unless a holistic scientific review of the case including all contributing clinical factors (antepartum, intrapartum and neonatal), fetal heart rate monitoring, neonatal MRI if possible (and preferred) or late MRI, and histology (placental histology if performed) are taken into account, success for plaintiff or defendant currently in a court of law will depend on eloquent legal argument rather than true scientific causality. The 10 criteria set out in this document to implicate acute intrapartum hypoxia in hypoxic ischaemic encephalopathy/neonatal encephalopathy serve as a guideline in the medicolegal setting

Insulin resistance induced by antiretroviral drugs: Current understanding of molecular mechanisms

The increase in incidence of HIV infection continues to be a major public health problem across the world, but more especially in sub-Saharan Africa. Treatment with highly active antiretroviral therapy (HAART) has improved the prognosis of patients with AIDS, but it has also increased the incidence of various metabolic disorders, in particular insulin resistance accompanied by dyslipidaemia, hyperglycaemia and lipodystrophy. This is often accompanied by frank type 2 diabetes and increased mortality from cardiovascular disease. It is important to understand the mechanistic basis for these side-effects as the incidence of these is likely to increase as the rollout of antiretroviral drugs continues

Optical products for refractive error and low vision

This article will focus on the optical products required for the efficient delivery of refractive error and low vision services, and provide insight into how they can be managed effectively to ensure a quality service. You can consult the IAPB Standard List (see page 30) for suggestions regarding the optical products you may require at your facility as well as recommended suppliers

‘Sink or swim?’: Learning from stories of becoming academics within a transforming university terrain

The meanings connected with becoming or being an academic are constantly shifting, on account of diverse forces that act on universities. The authors of this article portray their learning as a research team of four academics (including one early-career academic) and a doctoral student who took a narrative inquiry approach to listening and responding to their early-career colleagues’ stories of becoming and being academics within a transforming university landscape. Imaginative engagement with these stories through the evocative and reflexive medium of poetry awakened possibilities for navigating the uncertain terrain of academia. The article draws attention to collegial relationships as critical to the growth of self-belief and self-resourcefulness in becoming and being academics. It demonstrates how, through collective participation, novice and experienced academics can become valuable sources of learning and support for each other