Extending finite-memory determinacy to multi-player games

We show that under some general conditions the finite memory determinacy of a class of two-player win/lose games played on finite graphs implies the existence of a Nash equilibrium built from finite memory strategies for the corresponding class of multi-player multi-outcome games. This generalizes a previous result by Brihaye, De Pril and Schewe. We provide a number of example that separate the various criteria we explore.Our proofs are generally constructive, that is, provide upper bounds for the memory required, as well as algorithms to compute the relevant Nash equilibria

Water erosion risk assessment in South Africa : a proposed methodological framework

With the increase in human impacts on the environment, especially in terms of agricultural intensification and climate change, erosion processes need to be assessed and continually monitored. In many countries, but particularly in developing countries such as South Africa, standardized methodological frameworks that deliver comparable results across large areas as a baseline for regional scale monitoring are absent. Due to limitations of scale at which techniques can be applied and erosion processes assessed, this study describes a multi-process and multiscale approach for soil erosion risk assessment under South African conditions. The framework includes assessment of sheet-rill erosion at a national scale based on the principles and components defined in the Universal Soil Loss Equation; gully erosion in a large catchment located in the Eastern Cape Province by integrating 11 important factors into a GIS; and sediment migration for a research catchment near Wartburg in KwaZulu-Natal by means of the Soil andWater Assessment Tool. Three hierarchical levels are presented in the framework, illustrating the most feasible erosion assessment techniques and input datasets that are required for application at a regional scale with proper incorporation of the most important erosion contributing factors. The methodological framework is not interpreted as a single assessment technique but rather as an approach that guides the selection of appropriate techniques and datasets according to scale dependency and modelled complexity of the erosion processes.National Research Foundationhttp://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1468-0459hb201

Factors controlling gully development : comparing continuous and discontinuous gullies

Gully erosion is a degradation process affecting soils in many parts of theWorld. Despite the complexity of a series of collective factors across different spatial scales, previous research has not yet explicitly quantified factor dominance between different sized gullies. This factorial analysis quantifies the differences in factor dominance between continuous gullies (cgs) and discontinuous gullies (dgs). First, gullies (totaling 5273 ha) visible from SPOT 5 imagery were mapped for a catchment (nearly 5000 km2) located in the Eastern Cape Province of South Africa. Eleven important factors were integrated into a geographical information system including topographical variables, parent material-soil associations and land use–cover interactions. These were utilized in a zonal approach in order to determine the extent factors differ between cgs and dgs. Factors leading to the development of cgs are gentle footslopes in zones of saturation along drainage paths with a large contributing area, erodible duplex soils derived from mudstones and poor vegetation cover due to overgrazing. Compared to cgs conditions, more dgs occur on rolling slopes where the surface becomes less frequently saturated with a smaller contributing area, soils are more stable and shallow. Factorial analysis further illustrates that differences in factor dominance between the two groups of gullies is most apparent for soil factors. A combination of overgrazing and susceptible mudstones proves to be key factors that consistently determine the development of cgs and dgs.The ARC-ISCW, as well as Mr. D. J. Pretorius and his colleagues at the Department of Agriculture Forestry and Fisheries (DAFF), Directorate Land Use and Soil Management.http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1099-145X

Extending Finite Memory Determinacy to Multiplayer Games

We show that under some general conditions the finite memory determinacy of a class of two-player win/lose games played on finite graphs implies the existence of a Nash equilibrium built from finite memory strategies for the corresponding class of multi-player multi-outcome games. This generalizes a previous result by Brihaye, De Pril and Schewe. For most of our conditions we provide counterexamples showing that they cannot be dispensed with. Our proofs are generally constructive, that is, provide upper bounds for the memory required, as well as algorithms to compute the relevant winning strategies.Comment: In Proceedings SR 2016, arXiv:1607.0269

Determining the distribution of wetlands across Eswatini

Eswatini became a signatory to the Ramsar Convention on the 15th of June, 2013. To date, the country does not have a national wetland inventory. This study applies a newly developed wetland mapping technique (produced in South Africa) to Eswatini, to provide baseline information on the potential distribution of wetlands across the country. Results of this study show that when applying the mapping technique as it was applied in South Africa, watercourses (rivers, drainage lines, and riparian zones) are more frequently mapped than true wetlands. Given that Eswatini currently uses the broad Ramsar definition of a wetland, the potential wetland map produced in this study is well suited to identify wetlands falling under such definition. However, the technique does not suffice where a more specific definition for wetlands is used. To improve the initial potential wetland map, this study made use of data, obtained from 2 000 points distributed across the initial wetland map, by classifying areas with the highest potential of being wetlands into hydrogeomorphic units. Results indicate that the methods used to improve the initial map areable to distinguish watercourses with a higher potential of being a true wetland and identify certain hydrogeomorphic units. This method can therefore be used to provide baseline data of potential wetland distribution for countries that do not possess the means, or attribute data to produce a comprehensive wetland map.The Water Research Commission of South Africa; the University of Pretoria and the University of Eswatini.http://www.tandfonline.com/loi/rsag20hj2024Geography, Geoinformatics and MeteorologySDG-15:Life on lan

Psychologists’ experiences with telepsychology during the COVID-19 pandemic in South Africa

Background: During the COVID-19 pandemic, South African psychologists started to use telepsychology to continue providing services. However, diverse factors may influence psychologists’ decisions regarding the use of telepsychology. Aim: To investigate South African psychologists’ experiences with using telepsychology during the COVID-19 pandemic. Setting: Health Professions Council of South Africa (HPCSA)-registered psychologists practising in South Africa. Methods: A quantitative, cross-sectional study was conducted. Psychologists were invited to complete an online survey on the REDCap platform. Convenience sampling was used for respondent selection (n = 179). The study explored demographic variables, telepsychology use, changes in psychotherapy format, guidelines, ethical considerations, training, socio-economic factors, and individual patient and psychotherapist factors. Descriptive statistics, including categorical variables (frequencies and percentages) and numerical variables (medians and percentiles) were utilised for the data analysis. A bivariate analysis with backward selection was subsequently used, and significant variables were integrated into the logistic regression model. Results: Most respondents (84.8%) used telepsychology, with 72.8% considering it a positive experience. Private psychologists used electronic means for delivering services significantly more than public sector psychologists. The public sector psychologists had more challenges relating to changes in the therapeutic format, additional training requirements and technology access. Conclusion: During the COVID-19 pandemic, psychologists turned to telepsychology as a valuable tool for providing services while navigating the unique challenges it presented. Contribution: This study provides insights into the utility of telepsychology in the South African context during COVID-19. It underscores the experiences, importance of guidelines, and needs regarding training and technology access among psychologists

False Positive 18F-FDG Positron Emission Tomography Findings in Schwannoma—A Caution for Reporting Physicians

Schwannoma is a rare source of false-positive 18F-fluorodeoxyglucose (18F-FDG) uptake in Positron-emission tomography (PET/CT), inducing potential errors in staging of several solid cancer, with implications for patient management. This clinical case reports the situation of a patient undergoing an 18F-FDG-PET/CT for initial staging of an ovarian adenocarcinoma. We found a high paramediastinal hypermetabolic mass suspicious of remote extension or secondary synchronous primitive tumor. The biopsy finally reveals a histopathology of Schwannoma, allowing the patient to be eligible for a surgical procedure of her ovarian adenocarcinoma by rejecting the hypothesis of malignancy

Evolutionary-thinking in agricultural weed management

Agricultural weeds evolve in response to crop cultivation. Nevertheless, the central importance of evolutionary ecology for understanding weed invasion, persistence and management in agroecosystems is not widely acknowledged. This paper calls for more evolutionarily-enlightened weed management, in which management principles are informed by evolutionary biology to prevent or minimize weed adaptation and spread. As a first step, a greater knowledge of the extent, structure and significance of genetic variation within and between weed populations is required to fully assess the potential for weed adaptation. The evolution of resistance to herbicides is a classic example of weed adaptation. Even here, most research focuses on describing the physiological and molecular basis of resistance, rather than conducting studies to better understand the evolutionary dynamics of selection for resistance. We suggest approaches to increase the application of evolutionary-thinking to herbicide resistance research. Weed population dynamics models are increasingly important tools in weed management, yet these models often ignore intrapopulation and interpopulation variability, neglecting the potential for weed adaptation in response to management. Future agricultural weed management can benefit from greater integration of ecological and evolutionary principles to predict the long-term responses of weed populations to changing weed management, agricultural environments and global climate

Strain-induced Pockels effect in silicon waveguides

International audienc

High speed characteristics of strained-induced Pockels effect in silicon

International audienceWith the fast growing demand of data, current chip-scale communication systems based on electrical links suffer rate limitations and high power consumptions to address these new requirements. In this context, Silicon Photonics has proven to be a viable alternative by replacing electronic links with optical ones while taking advantage of the well-established CMOS foundries techniques to reduce fabrication costs. However, silicon, in spite of being an excellent material to guide light, its centrosymmetry prevents second order nonlinear effects to exist, such as Pockels effect an electro-optic effect extensively used in high speed and low power consumption data transmission. Nevertheless, straining silicon by means of stressed thin films allows breaking the crystal symmetry and eventually enhancing Pockels effect. However the semiconductor nature of silicon makes the analysis of Pockels effect a challenging task because free carriers have a direct impact, through plasma dispersion effect, on its efficiency, which in turn complicates the estimation of the second order susceptibility necessary for further optimizations. However, this analysis is more relaxed working in high-speed regime because of the frequency limitation of free carriers-based modulation. In this work, we report experimental results on the modulation characteristics based on Mach-Zehnder interferometers strained by silicon nitride. We demonstrated high speed Pockels-based optical modulation up to 25 GHz in the C-band