The Effect Of Training Frequency On Selected Physical And Biochemical Health Parameters In The Conditioning And Reconditioning Of Sedentary Employees

Non-communicable disease evolved as a major health risk in South Africa and accounts for about 37% of all deaths. This burden also challenges human resources in the corporate environment where poor health status (high health risks) may lead to increased health care costs, lowered productivity and eventually to premature death. Some of the South African companies have tackled this challenge by providing various employee health promotion initiatives. One of the popular contributions in this endeavour is to encourage employees to become more physically active in order to prevent detrimental health risk factors or to remedy the existing factors. A major challenge in this initiative is to keep up the compliance of the employees with their physical conditioning programmes, especially when business responsibilities take them away from their health facilities which, in turn, may lead to physical deconditioning. This endorses the motivation of this research as little information is available in South Africa on the aspect of conditioning, deconditioning and reconditioning in the corporate environment. In this study, 60 healthy but sedentary employees, ages 28-49 years, from an academic institution were recruited to participate. They were randomly assigned to three groups, where Groups A and B form the experimental groups with Group C the control group. During the initial training phase (first 12 weeks) Group A and B followed a training frequency of three times per week, while retraining took place at a frequency of two and four times per week for Groups A and B, respectively. Group C was not involved in any intervention and continued with their normal daily activities and lifestyle. Results of this study indicated that after training at a program frequency of three times per week, a salutogenic response occurred in the selected physical and biochemical health parameters. With deconditioning, about 50% of the physical benefits were lost, which occurred faster than the decline in the biochemical (lipids) benefits. With reconditioning, a program frequency of two times per week seems to maintain the physiological status, while with a program frequency of four times per week, an improvement reoccurred, exceeding the benefits of the program frequency of three times per week. In conclusion, it is clear that a physical intervention regime, to the apparently healthy employees, can decrease some health risks; but with an interruption of the program, salutogenic benefits will be partially lost. With retraining, a program frequency of two times per week will not produce significant improvement, but will only maintain the physical status

GPS TEC and ionosonde TEC over Grahamstown, South Africa: first comparisons

The Grahamstown, South Africa (33.3°S, 26.5°E) ionospheric field station operates a UMass Lowell digital pulse ionospheric sounder (Digisonde) and an Ashtech geodetic grade dual frequency GPS receiver. The GPS receiver is owned by Chief Directorate Surveys and Mapping (CDSM) in Cape Town, forms part of the national TrigNet network and was installed in February 2005. The sampling rates of the GPS receiver and Digisonde were set to 1 s and 15 min, respectively. Data from four continuous months, March–June 2005 inclusive, were considered in this initial investigation. Data available from the Grahamstown GPS receiver was limited, and, therefore, only these 4 months have been considered. Total Electron Content (TEC) values were determined from GPS measurements obtained from satellites passing near vertical (within an 80° elevation) to the station. TEC values were obtained from ionograms recorded at times within 5 min of the near vertical GPS measurement. The GPS derived TEC values are referred to as GTEC and the ionogram derived TEC values as ITEC. Comparisons of GTEC and ITEC values are presented in this paper. The differential clock biases of the GPS satellites and receivers are taken into account. The plasmaspheric contribution to the TEC can be inferred from the results, and confirm findings obtained by other groups. This paper describes the groundwork for a procedure that will allow the validation of GPS derived ionospheric information with ionosonde data. This work will be of interest to the International Reference Ionosphere (IRI) community since GPS receivers are becoming recognised as another source for ionospheric information

A recurrent neural network approach to quantitatively studying solar wind effects on TEC derived from GPS; preliminary results

This paper attempts to describe the search for the parameter(s) to represent solar wind effects in Global Positioning System total electron content (GPS TEC) modelling using the technique of neural networks (NNs). A study is carried out by including solar wind velocity (Vsw), proton number density (Np) and the Bz component of the interplanetary magnetic field (IMF Bz) obtained from the Advanced Composition Explorer (ACE) satellite as separate inputs to the NN each along with day number of the year (DN), hour (HR), a 4-month running mean of the daily sunspot number (R4) and the running mean of the previous eight 3-hourly magnetic A index values (A8). Hourly GPS TEC values derived from a dual frequency receiver located at Sutherland (32.38° S, 20.81° E), South Africa for 8 years (2000–2007) have been used to train the Elman neural network (ENN) and the result has been used to predict TEC variations for a GPS station located at Cape Town (33.95° S, 18.47° E). Quantitative results indicate that each of the parameters considered may have some degree of influence on GPS TEC at certain periods although a decrease in prediction accuracy is also observed for some parameters for different days and seasons. It is also evident that there is still a difficulty in predicting TEC values during disturbed conditions. The improvements and degradation in prediction accuracies are both close to the benchmark values which lends weight to the belief that diurnal, seasonal, solar and magnetic variabilities may be the major determinants of TEC variability

Towards a GPS-based TEC prediction model for Southern Africa with feed forward networks

In this paper, first results from a national Global Positioning System (GPS) based total electron content (TEC) prediction model over South Africa are presented. Data for 10 GPS receiver stations distributed through out the country were used to train a feed forward neural network (NN) over an interval of at most five years. In the NN training, validating and testing processes, five factors which are well known to influence TEC variability namely diurnal variation, seasonal variation, magnetic activity, solar activity and the geographic position of the GPS receivers were included in the NN model. The database consisted of 1-min data and therefore the NN model developed can be used to forecast TEC values 1 min in advance. Results from the NN national model (NM) were compared with hourly TEC values generated by the earlier developed NN single station models (SSMs) at Sutherland (32.38°S, 20.81°E) and Springbok (29.67°S, 17.88°E), to predict TEC variations over the Cape Town (33.95°S, 18.47°E) and Upington (28.41°S, 21.26°E) stations, respectively, during equinoxes and solstices. This revealed that, on average, the NM led to an improvement in TEC prediction accuracy compared to the SSMs for the considered testing periods

Application of neural networks to South African GPS TEC modelling

The propagation of radio signals in the Earth’s atmosphere is dominantly affected by the ionosphere due to its dispersive nature. Global Positioning System (GPS) data provides relevant information that leads to the derivation of total electron content (TEC) which can be considered as the ionosphere’s measure of ionisation. This paper presents part of a feasibility study for the development of a Neural Network (NN) based model for the prediction of South African GPS derived TEC. The South African GPS receiver network is operated and maintained by the Chief Directorate Surveys and Mapping (CDSM) in Cape Town, South Africa. Vertical total electron content (VTEC) was calculated for four GPS receiver stations using the Adjusted Spherical Harmonic (ASHA) model. Factors that influence TEC were then identified and used to derive input parameters for the NN. The well established factors used are seasonal variation, diurnal variation, solar activity and magnetic activity. Comparison of diurnal predicted TEC values from both the NN model and the International Reference Ionosphere (IRI-2001) with GPS TEC revealed that the IRI provides more accurate predictions than the NN model during the spring equinoxes. However, on average the NN model predicts GPS TEC more accurately than the IRI model over the GPS locations considered within South Africa

Reconstructing ionospheric TEC over South Africa using signals from a regional GPS network

Radio signals transmitted by GPS satellites orbiting the Earth are modulated as they propagate through the electrically charged plasmasphere and ionosphere in the near-Earth space environment. Through a linear combination of GPS range and phase measurements observed on two carrier frequencies by terrestrial-based GPS receivers, the ionospheric total electron content (TEC) along oblique GPS signal paths may be quantified. Simultaneous observations of signals transmitted by multiple GPS satellites and observed from a network of South African dual frequency GPS receivers, constitute a spatially dense ionospheric measurement source over the region. A new methodology, based on an adjusted spherical harmonic (ASHA) expansion, was developed to estimate diurnal vertical TEC over the region using GPS observations over the region. The performance of the ASHA methodology to estimate diurnal TEC and satellite and receiver differential clock biases (DCBs) for a single GPS receiver was first tested with simulation data and subsequently applied to observed GPS data. The resulting diurnal TEC profiles estimated from GPS observations compared favourably to measurements from three South African ionosondes and two other GPS-based methodologies for 2006 solstice and equinox dates. The ASHA methodology was applied to calculating diurnal two-dimensional TEC maps from multiple receivers in the South African GPS network. The space physics application of the newly developed methodology was demonstrated by investigating the ionosphere’s behaviour during a severe geomagnetic storm and investigating the long-term ionospheric stability in support of the proposed Square Kilometre Array (SKA) radio astronomy project. The feasibility of employing the newly developed technique in an operational near real-time system for estimating and dissimenating TEC values over Southern Africa using observations from a regional GPS receiver network, was investigated

Development of a regional GPS-based ionospheric TEC model for South Africa

Advances in South African space physics research and related disciplines require better spatial and time resolution ionospheric information than was previously possible with the existing ionosonde network. A GPS-based, variable degree adjusted spherical harmonic (ASHA) model was developed for near real-time regional ionospheric total electron content (TEC) mapping over South Africa. Slant TEC values along oblique GPS signal paths are quantified from a network of GPS receivers and converted to vertical TEC by means of the single layer mapping function. The ASHA model coefficients and GPS differential biases are estimated from vertical TEC at the ionospheric pierce points and used to interpolate TEC at any location within the region of interest. Diurnal TEC variations with one minute time resolution and time-varying 2D regional TEC maps are constructed. In order to validate the ASHA method, simulations with an IRI ionosphere were performed, while the ASHA results from actual data were compared with two independent GPS-based methodologies and measured ionosonde data

Malondialdehyde Acetaldehyde Adducts (MAA-Adducts) Direct Distinctive Pro-Inflammatory Responses in Endothelial and Macrophage Cell Lines

Chronic inflammation plays a critical role in the pathogenesis of atherosclerosis. At present, the mechanism(s) by which inflammation contributes to this disease isnot entirely understood. Inflammation is known to induce oxidative stress, of which one consequence is lipid peroxidation. This process leads to the production of malondialdehyde (MDA), which can subsequently break down to form acetaldehyde (AA). These two aldehyde by-products can covalently interact with the ε-amino group of lysineswithin proteins and lipoproteins leading to the formation of highly immunogenic malondialdehyde-acetaldehyde adducts (MAA-adducts). The aim of this study was to determine the in-vitro cytokine response of endothelial cells and macrophages treated with MAA-modified human serum albumin (HSA-MAA) and low-density lipoprotein (LDL-MAA). In addition, cells isolated from mice with exposure to MAA and high fat diets were stained and imaged for uptake of the modified macromolecules of interest. We found that exposure of endothelial cells resulted in increased expression of IL-6, TNF-α, ICAM-1, VCAM-1, and MCP-1 in response to incubation with HSA-MAA; whereas, the same treatment of macrophages resulted in increased expression of IL-6, TNF-α, and IL-1b. LDL-MAA incubationresulted in increased TNF-α expression in macrophages, but MCP-1 was elevated in endothelial cells. Interestingly, the quantitative and qualitative uptake of triglycerides was increased in both endothelial and macrophage cells when exposed to LDL-MAA compared to LDL alone. The results of these studies demonstrate that different MAA-adducts elicit unique responses in different cell types. Additionally, the presence of MAA appears to modulate the cells leading to increased uptake of triglycerides and further progression of the inflammatory response.https://digitalcommons.unmc.edu/emet_posters/1003/thumbnail.jp

Present day challenges in understanding the geomagnetic hazard to national power grids

Power grids and pipeline networks at all latitudes are known to be at risk from the natural hazard of geomagnetically induced currents. At a recent workshop in South Africa, UK and South African scientists and engineers discussed the current understanding of this hazard, as it affects major power systems in Europe and Africa. They also summarised, to better inform the public and industry, what can be said with some certainty about the hazard and what research is yet required to develop useful tools for geomagnetic hazard mitigation