Variations of Particle Motion in the Van Allen Belts

Earth's magnetic field traps charged particles from the solar wind in the Van Allen belts. These trapped ions execute three types of motion: helical motion around magnetic field lines, longitudinal motion between North and South mirror points, and latitudinal drift motion around Earth. Each is associated with an adiabatic invariant, which expresses restrictions on each type of motion. This study examines the effect on proton motion and the three adiabatic invariants when the strength of Earth's magnetic moment varies with time. Using a Python 3 code developed in Google Colaboratory, each invariant was calculated and graphed for a static magnetic field, for magnetic fields that varied with periods shorter than the invariant period, and for magnetic fields that varied with periods longer than the invariant period. The results demonstrate that if Earth's magnetic moment changes quickly enough with time, the adiabatic invariant is no longer constant, allowing a wider variety of ion movement. Further study of these invariants and how they change in time-varying magnetic fields could help predict ion motion and changes to the magnetosphere during events that affect space weather, like solar storms or pole reversals

Do employees' perceptions of HR practices in South African firms affect their subsequent turnover destinations?

Employee turnover is an ongoing issue in organisations because it has long been thought to detriment overall organisational efficiency and performance (Lee, Gerhart, Weller & Trevor, 2008; Takeuchi, Chen & Lepak, 2009; Trevor, 2001). Managers are only able to observe and control some aspects or influencers of turnover (Dalton, Todor & Krackhardt, 1982). Placing voluntary turnover drivers in context with human resource (HR) practices might provide a means through which managers can understand the less visible aspects of turnover. HR practices may assist managers to reduce the controllable (evident) and less observable drivers of voluntary turnover. March and Simon (1958), the seminal employee turnover theorists, suggest that the voluntary turnover decision has two competing aspects – desirability of the current job and desirability of alternatives. The perceived utility an employee garners from the current job might define the desirability of the current job. The more desirable the current job, the greater satisfaction and lower the likelihood of a quit. The potential utility the individual deems available from perceived alternative opportunities might define the desirability of alternatives. If the potential utility of an alternative outweighs the utility garnered by the current job, a quit seems more likely (March & Simon, 1958). Generally, mainstream voluntary turnover research has placed emphasis on understanding turnover antecedents in the current organisation - the aspects that lower the perceived utility garnered by the current job (Kirschenbaum & Weisberg, 2002). However, considerably less research has focused on the alternative that draws the employee away from their current job (Kirschenbaum & Weisberg, 2002). The alternative to which the individual moves is the turnover destination. The turnover destination contributes towards the withdrawal process because the person perceived the alternative as more desirable than the current job, increasing the likelihood of a quit. Observing organisational performance may provide an important means through which to examine the effect turnover destinations may have on withdrawal. Strategic human resource management (SHRM) and similar organisational development fields hold a particular view on organisational performance. SHRM theorists have paid particular attention to the implementation of high-performance human resource (HR) practices in organisations. Predominantly, extensive research has been conducted on the effect highiii performance HR practices might have on organisational performance and retention. SHRM theorists suggest that a combination (system) of high-performance HR practices correctly implemented in the firm, and aligned with organisational strategy, should bring about improved organisational performance and employee retention (Arthur, 1994; Carmeli & Schaubroeck, 2005; Combs, Liu, Hall & Ketchen, 2006; Shaw, Gupta & Delery, 2005; Subramony, 2009; Youndt, Snell, Dean & Lepak, 1996; Wood, 1999). The field of turnover destination research highlights the role of turnover destinations in the voluntary turnover process. Specifically, turnover destination theorists postulate that antecedents present in the current firm affect the quit decision by influencing the intensity of the desire to leave, and the perception of alternative opportunities shapes the choice of turnover destination (Kirschenbaum & Mano-Negrin, 1999; Kirschenbaum & Weisberg, 2002). Research in the field focuses on the influence turnover destinations might have on turnover intentions, moving away from the traditional focus of internal organisational antecedents and personal factors (Kirschenbaum & Weisberg, 2002). The relationship between high-performance HR practices and turnover destinations has not been extensively tested empirically, with few known studies in existence (for example: Fields, Dingman, Roman & Blum, 2005). Therefore, there is opportunity for greater research in the field. The developing South African economy is a suitable environment in which to measure whether high-performance HR practices affect turnover destinations at the individual-level, as no known research has been conducted. The South African economy is said to be suffering from the mass emigration of highly skilled individuals, who mostly move to developed countries with less prominent societal issues and less restrictive labour policies, amongst other reasons (Kerr-Phillips & Thomas, 2009; McDonald & Crush, 2002). A key interest for this research is the role experience of highperformance HR practices might play in emigration of South African white-collar workers. The study explores the relationship between high-performance HR practices and turnover destinations by measuring met expectations and turnover intentions. The objective of the empirical study is to establish whether experience of high-performance HR practices in the current job affect the likelihood of particular turnover destinations. A quantitative study, using a two-part time-separated survey, was conducted on white-collar workers from three South African provinces, including Gauteng, Kwa-Zulu iv Natal and the Western Cape. The first part of the survey measured respondents’ perceptions of the levels of actual high-performance HR practice provision in the current organisation. In addition, respondent expectations about the adequate level of the practices (that should retain them in their current jobs) were measured. The second part of the survey measured respondents’ intentions to move into a predefined set of turnover destinations. The final sample of 386 participants was used to analyse the impact of interactions between actual and adequate high-performance HR practices on a variety of turnover destinations, using polynomial regression analysis and response surface methodology. Overall, the results showed that a system of high-performance HR practices exert a weak to moderate influence on the predefined turnover destinations. Generally, South Africans with lower expectations about high-performance HR practice provision appear less likely to leave a job when the employer places greater emphasis on the practices. However, the likelihood of internal transfer and moving into a different organisation increases for individuals who possess higher expectations about high-performance HR practice provision, and have experienced higher levels of actual provision. The findings also show that, for the most part, the likelihood of emigration increases in employees with lower actual provision of high-performance HR practices, largely contradicting expectations about emigration. The increase in the likelihood of internal transfers and moves to external organisations, despite higher actual high-performance HR practice provision, might point towards over-provision of the practices, or the possibility of continuance commitment in South African employees. The findings suggest that, rather than higher emphasis of highperformance HR practices providing a means for emigration, broader external societal conditions may be motivating the emigration of skilled South Africans. As the results showed that a set of high-performance HR practices may exert a weak to moderate influence on turnover destination selection, there are recommendations for managers and future research. Implications for managers include promoting the implementation of a set of high-performance HR practices in the organisation. Researchers in the turnover destinations field should endeavour to measure actual turnover, rather than intentions in future studies

Effect of dolerite intrusions on coal quality in the Secunda coal fields of South Africa

The coalfields of South Africa contain numerous dolerite intrusions, which are believed to have affected the quality of the surrounding coal by a thermal process, controlled by the size of the magmatic body. Data gathered from a working coalfield in Secunda, South Africa, suggest that the relationship between intrusive sills and coal is complex and factors other than intrusion width must be considered in relation to the contact metamorphic effect. The study area contains multiple dolerite intrusions of Karoo age, separated according to their geometric relationship to the local coal seams. Three intrusions were selected for detailed study. The three dolerite bodies, namely the DO4, DO8 and DO10 dolerites, occur as sills intruded close to the main coal seam of the area. The dolerite sills have identical mineralogy and can only be distinguished through textural variations in thin section. Coal quality data was obtained from Sasol Mining Secunda and used to investigate the presence or absence of a change in coal quality relative to dolerite proximity. Reduction in coal quality was defined using three main proximate analysis values, termed Ash, Volatile content (Vols) and Dry Ash Free Volatile (DAFV) in the coal industry. These parameters were used to determine the extent of any effect deleterious to coal quality induced by the intrusion of the dolerite sills. The resultant investigation showed no correlation between the position and thickness of the dolerites, and a change in coal quality (as measured by proximate analysis). In the absence of a linear relationship between coal quality and dolerite proximity, two processes are proposed to explain the absence of the contact metamorphic effects expected from previous studies: -Dolerite emplacement dynamics may influence the size of the metamorphic aureole produced by an intrusion, and invalidating intrusion size as a measure of thermal output, - Hydrothermal fluids mobilised by the dolerite intrusions, either from the country rock or the intrusion itself may percolate through the coal and act as the metamorphic agent responsible for changing coal quality, by dissolving the volatile components of the coal and transporting them to other locations These two processes are sufficient to explain the lack of a clear “metamorphic effect” related to the dolerite intrusions. CopyrightDissertation (MSc)--University of Pretoria, 2012.Geologyunrestricte

A large scale investigation into changes in coal quality caused by dolerite dykes in Secunda, South Africa-implications for the use of proximate analysis on a working mine

The coalfields of South Africa contain numerous dolerite intrusions, which affected the quality of the surrounding coal through thermal processes, commonly believed to be controlled by the size of the magmatic body. Data gathered from a working coalfield in Secunda, South Africa, suggest that the relationship between intrusive sills and coal is complex and factors other than intrusion width must be considered in relation to the contact metamorphic effect. The study area contains multiple dolerite intrusions of Karoo age, of which three intrusions occur as sills intruded close to the main coal seam of the. A large database (>8000 boreholes) of coal quality data was used to investigate the presence or absence of a change in coal quality relative to dolerite proximity. Reduction in coal quality was defined using three proximate analysis values, namely the ash, volatile content and dry ash free volatile (DAFV) as defined in the coal industry. The resultant investigation showed no correlation between the position and thickness of the dolerites, and changes in coal quality as measured by proximate analysis. In the absence of a linear relationship between coal quality and dolerite proximity, two processes are proposed to explain the absence of the contact metamorphic effects expected from previous studies. Firstly dolerite emplacement dynamics may influence the size of the metamorphic aureole produced by an intrusion, invalidating intrusion size as a measure of thermal output. Secondly, hydrothermal fluids mobilised by the dolerite intrusions, either from the country rock or the intrusion itself may percolate through the coal and act as the metamorphic agent responsible for changing coal quality, by dissolving the volatile and semi-volatile components of the coal and transporting them to other locations. These two processes are sufficient to explain the lack of a clear “metamorphic effect” related to the dolerite intrusions. However, the perceived lack of a clear correlation between the coal quality parameters and the metamorphic effects associated with dolerite intrusion may also reflect the inadequacies of proximate analysis techniques in quantifying geological processes within the coal.Coaltech research organisation.http://www.elsevier.com/locate/jafrearsci2017-05-31hb2016Geolog

The implementation of the South African Orthopaedic Registry (SAOR) : factors that improve usage

BACKGROUND : Registries have been created to accrue comprehensive clinical data for evaluation, with purported benefits for clinical governance, public health and scientific investigation. As has been the experience internationally, orthopaedic surgeon contribution to data collection for the South African Orthopaedic Registry (SAOR) has been moderate. Due to this response, several awareness initiatives were implemented by the South African Orthopaedic Association (SAOA) to encourage surgeons to engage with SAOR. This study aimed to evaluate the efficacy of these initiatives. METHODS: This retrospective study evaluated SAOR’s operational data between 1 August 2019 and 30 June 2022. For each month, the number of new surgeons registering, new patients captured, and new registry pathways initiated were evaluated. These monthly increases were evaluated relative to the implementation of several awareness initiatives. Multiple linear regression was performed to determine if any initiative significantly increased recruitment rates. The Strengthening the Reporting of Observational studies in Epidemiology (STROBE) checklist was used for reporting. RESULTS: Thirty-five months of SAOR operational data were analysed. The cumulative number of surgeons enrolled to use the registry by June 2022 was 108, the number of patients captured 9 992, and the number of pathways initiated 9 585. Thirty-three awareness initiatives of four types took place in the period from January 2021 until June 2022. No interventions increased the recruitment of surgeons. Group promotional sessions and virtual group demonstrations significantly increased the number of patients captured on the registry. Group promotional sessions significantly increased the number of pathways initiated. CONCLUSION: The SAOR was established in 2019 by the SAOA with the intent to improve orthopaedic practice in South Africa. Several awareness initiatives have been implemented to engage surgeon contributions to the registry, none of which increased enrolment of new surgeons, but some of which increased the number of patients captured and pathways initiated. Ways to improve surgeon engagement with registries should be the focus of future research.https://www.saoj.org.za/index.php/saojOrthopaedic SurgerySDG-03:Good heatlh and well-beingSDG-09: Industry, innovation and infrastructur

Physicochemical analysis of South African metamorphosed coal

An in-depth understanding of the physico-chemical nature of coal is required in order to meet ever-increasing energy demands and environmental legislature. New and classical coal analysis techniques were used on thermally-affected coals from a working coalfield in Secunda, South Africa. The study area has ubiquitous dolerite intrusions that have large-scale impacts on the minable coal resource. A combination of five modern and classical analysis techniques, namely Schmidt hammer testing, three-dimensional X-ray tomography, proximate analysis, petrographic analysis with reflectance analysis, and two-dimensional gas chromatography time of flight mass spectrometry (GC*GCTOFMS) were used to model the mechanics of metamorphism of coal intruded by an igneous body. Freshly exposed coalface with an intersecting dolerite was analysed. The data produced from GC*GCTOFMS, reflectance, and tomographic analysis produced no strong linear correlations. Thermal dolerite influence was capped at approximately 5m from the dolerite intrusion and of note was a secondary trend that identified peaks throughout the transect correlating across GC*GCTOFMS, reflectance, and tomographic analysis. To reconcile the non-linear correlation a model using a combination of hydrothermal and thermal influences was produced to explain the mechanics of the metamorphic environment.Thesis (PhD)--University of Pretoria 2020.GeologyPhDUnrestricte

Los problemas del trabajo : productividad y automación

Fil: Bussio, Aníbal Ricardo