3,960 research outputs found
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
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
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 and the phase
function asymmetry factor with a value of 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
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