A Finite Element Model for Describing the Effect of Muscle Shortening on Surface EMG

A finite-element model for the generation of single fiber action potentials in a muscle undergoing various degrees of fiber shortening is developed. The muscle is assumed fusiform with muscle fibers following a curvilinear path described by a Gaussian function. Different degrees of fiber shortening are simulated by changing the parameters of the fiber path and maintaining the volume of the muscle constant. The conductivity tensor is adapted to the muscle fiber orientation. In each point of the volume conductor, the conductivity of the muscle tissue in the direction of the fiber is larger than that in the transversal direction. Thus, the conductivity tensor changes point-by-point with fiber shortening, adapting to the fiber paths. An analytical derivation of the conductivity tensor is provided. The volume conductor is then studied with a finite-element approach using the analytically derived conductivity tensor. Representative simulations of single fiber action potentials with the muscle at different degrees of shortening are presented. It is shown that the geometrical changes in the muscle, which imply changes in the conductivity tensor, determine important variations in action potential shape, thus affecting its amplitude and frequency content. The model provides a new tool for interpreting surface EMG signal features with changes in muscle geometry, as it happens during dynamic contractions

The association between levels of socio-economic status and fibrin network architecture in women aged between 35 and 44 years

ThesisProspective epidemiological studies from 1980 to 1989 accumulated evidence of a possible relationship between cardiovascular disease and plasma fibrinogen concentration. It was soon evident that raised fibrinogen levels, causing hypercoagulable states, involve complex and multifactorial processes·. Consequently it is important to realise that hypercoagulability is associated with other risk factors of cardiovascular disease. This elevates the increasing importance of studying the haemostatic variables together with these risk factors. It is suspected however, that not only fibrinogen concentration, but also the quality of fibrin networks may contribute to coronary heart disease risk. It is known that other modulating factors in blood also affect the network structures as they are formed with otherwise constant fibrinogen and thrombin concentrations. Previous research extensively studied modulating factors such as albumin, glucose, smoking and diabetes. Socially patterned accumulation of health capital and cardiovascular risk begins in childhood. In the Whitehall II longitudinal study conducted by Brunner, adult occupational position was inversely associated with fibrinogen, other metabolic risk factors and risk factors like leisure time physical inactivity. Childhood, social position was associated with adult fibrinogen levels. The objective of this study was to determine the association between fibrin network architecture and socio-economic status in adult women. Three groups of adult women representing different socio-economic backgrounds were chosen randomly to voluntarily participate in the study. The study groups consisted of 27 white women (employees of the TFS), 30 "urbanized" black women (women living in an urbanized area for more than thirty years), and 30 "less urbanized" black women (women living in an urbanized area for less than thirty years). Fasting blood samples were taken on the premises of the Technikon Free State by a registered nurse and volunteers had medical examinations by a registered general practitioner. Fibrin network architecture variables and plasma fibrinogen were determined on fresh essentially platelet free plasma by standardised laboratory techniques. Other metabolic variables were performed on serum and full blood counts were performed on EDT A whole blood using standardised laboratory techniques. Results indicated that a association between socio-economic status and haemostatic profiles do exist. Many of the differences in analytical variables however, were expected and due to other relating factors such as ethnicity. The mean fibrinogen level of the white group of women was 3.S4±0.24 gIL. The group of black women defined as "less urbanized" displayed lower mean fibrinogen levels (3.16±.0.19 gIL). In contrast, the levels of the "urbanized" black women were much higher (4.04±0.22 gIL). However, these differences were not significant. This confirms the effect of urbanization and thus socio-economic status on plasma fibrinogen levels. Small differences were observed between network fibrin content and fibrinogen levels, and between mass length ratio and fibrinogen levels in all three the groups. It was unknown if these differences were static or in the process of development and an indication of future tendencies. Except for total protein values no significant differences were found between metabolic variables. This was expected as very strict inclusion/exclusion criteria were used to ensure that all volunteers were "apparently" healthy. This study in a way contradicts the hypothesis that socio-economic class itself may be the main cause of differences in some metabolic parameters from individuals within different levels of socio-economic backgrounds seeing as such strict exclusion criteria were used. It is believed that the factors related to the different levels of socio-economic status, such as the prevalence of tuberculosis, HIV, diabetes mellitus, hypercholesterolaemia, may play an important role in the outcome of the health status of the individuals within different levels of society. This study implies that the metabolic variables associated with different levels of socio-economic status are not necessarily associated with socio-economic class itself, but rather with the associated factors related to the different levels of socio-economic status. The study group was also very small which might have contributed to the lack of significance between groups. This study emphasises the need for prospective epidemiological trails to evaluate the true effect of socioeconomic variables and associated conditions on metabolic risk factors

On M. H. Hertz's Experiments

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Whose language is it anyway? Students’ sense of belonging and role of English for Higher Education in the multilingual, South African context

The current decolonial commitments in Higher Education necessitate a need to deepen our understanding of the relationship between English as a Medium of Instruction (EMI) and students’ sense of belonging, their identity, and epistemological access. This article investigates how EMI influences students’ personal and academic identities as well as their sense of belonging to the higher education space. Using student focus groups, this study is exploratory in nature and informed by the voices of undergraduate and postgraduate Humanities students at a South African university in the Free State. The responses were mixed, but there was general consensus that although English does have a place in higher education and can contribute to their sense of belonging, it also has an adverse effect on their identity; the use of indigenous languages provides them with greater epistemological access. A differentiated approach to multilingualism is a possible way forward

Bayesian inference of initial models in cryo-electron microscopy using pseudo-atoms.

Single-particle cryo-electron microscopy is widely used to study the structure of macromolecular assemblies. Tens of thousands of noisy two-dimensional images of the macromolecular assembly viewed from different directions are used to infer its three-dimensional structure. The first step is to estimate a low-resolution initial model and initial image orientations. This is a challenging global optimization problem with many unknowns, including an unknown orientation for each two-dimensional image. Obtaining a good initial model is crucial for the success of the subsequent refinement step. We introduce a probabilistic algorithm for estimating an initial model. The algorithm is fast, has very few algorithmic parameters, and yields information about the precision of estimated model parameters in addition to the parameters themselves. Our algorithm uses a pseudo-atomic model to represent the low-resolution three-dimensional structure, with isotropic Gaussian components as moveable pseudo-atoms. This leads to a significant reduction in the number of parameters needed to represent the three-dimensional structure, and a simplified way of computing two-dimensional projections. It also contributes to the speed of the algorithm. We combine the estimation of the unknown three-dimensional structure and image orientations in a Bayesian framework. This ensures that there are very few parameters to set, and specifies how to combine different types of prior information about the structure with the given data in a systematic way. To estimate the model parameters we use Markov chain Monte Carlo sampling. The advantage is that instead of just obtaining point estimates of model parameters, we obtain an ensemble of models revealing the precision of the estimated parameters. We demonstrate the algorithm on both simulated and real data

The assessment of intravascular volume

No Abstrac

Penerapan Prinsip Good Governance Terhadap Kualitas Pelayanan Publik

This study aims to determine the application of the principles of good governance, the quality of public services, and the effect of applying the principles of good governance on the quality of public services at the Makassar City Land Office. This research is a quantitative descriptive study using incidental sampling techniques. The data was collected by using a questionnaire, conducting interviews, observation, and documentation. The data analysis technique used is descriptive statistical analysis and inferential statistics (product moment correlation test) using the SPSS 18 application. The results of the descriptive analysis show that the application of the principles of good governance and the quality of public services at the Makassar City Land Office belongs to the good category in terms of indicator measuring the variable. The result of the product moment correlation analysis shows that the effect of the application of the principles of good governance governance on the quality of public services is 0.790, which is positive, which means that the level of influence is in the strong category

On-the-fly memory compression for multibody algorithms.

Memory and bandwidth demands challenge developers of particle-based codes that have to scale on new architectures, as the growth of concurrency outperforms improvements in memory access facilities, as the memory per core tends to stagnate, and as communication networks cannot increase bandwidth arbitrary. We propose to analyse each particle of such a code to find out whether a hierarchical data representation storing data with reduced precision caps the memory demands without exceeding given error bounds. For admissible candidates, we perform this compression and thus reduce the pressure on the memory subsystem, lower the total memory footprint and reduce the data to be exchanged via MPI. Notably, our analysis and transformation changes the data compression dynamically, i.e. the choice of data format follows the solution characteristics, and it does not require us to alter the core simulation code

Measurement of Dust Optical Properties in Coalsack

We have used FUSE and Voyager observations of dust scattered starlight in the neighborhood of the Coalsack Nebula to derive the optical constants of the dust grains. The albedo is consistent with a value of $0.28 \pm 0.04$ and the phase function asymmetry factor with a value of $0.61 \pm 0.07$ throughout the spectral range from 900 -- 1200 \AA, in agreement with previous determinations as well as theoretical predictions. We have now observed two regions (Ophiuchus and Coalsack) with intense diffuse background radiation and in both cases have found that the emission is due to light from nearby hot stars scattered by a relatively thin foreground cloud, with negligible contribution from the background molecular cloud.Comment: Total 19 pages, Figures 9, Accepted for publication in Astrophysical Journa

Student review of doctor-patient communication skills training in a South African undergraduate medical programme

Background. Barriers to the training of doctor-patient communication in the South African (SA) context have been well explored through qualitative research at several SA medical schools. However, this aspect of training has not been reviewed in a systematic way by a large number of students. A student review of doctor-patient communication skills training in the undergraduate medical programme of a medical school in SA was obtained to improve training and identify further research needs. Objective. To investigate doctor-patient communication skills training in the undergraduate programme of a medical school in SA to identify shortcomings and further research needs. Methods. A descriptive, cross-sectional design was used. Data were collected through an anonymous questionnaire based on Harden’s extended vision of the curriculum. Printed anonymous questionnaires, distributed to all the fourth- and fifth-year undergraduate medical students, were analysed quantitatively. Open-ended questions were analysed qualitatively using grounded theory. Results. The sample comprised 106/132 fifth-year students (response rate 80.3%) and 65/120 fourth-year students (response rate 54.2%). Frequent training in history-taking was reported by >75% of students, while >60% reported infrequent training in breaking bad news. More than 50% of participants indicated that senior doctors seldom or never modelled patient-centred communication in the clinical teaching milieu. Students preferred experiential learning to didactic methods. Conclusion. Medical students want to see patient-centred communication unequivocally modelled in the clinical setting. A greater emphasis on practical training in context-specific communication skills is required. Positive role-modelling is needed in the clinical environment