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

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

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

Bone intake by vultures in Namibia

The use of bones by vultures was assessed during early 2005 in the Otjiwarongo area in north-central Namibia. Bone fragments were utilized by all species, especially by the African White-backed Vulture Gyps africanus and the Lappet-faced Vulture Torgos tracheliotos. There was an overall increase in bone fragment consumption from May onwards (taken as the beginning of the breeding period). A rough estimate of bone fragment use for all vultures of 2.49 g/vulture (consumption/total number of vultures observed) and 60.31 g/vulture (consumption/individuals of vultures observed) was determined. The results suggest that bone fragments should be added as a supplement at vulture restaurants.Vulture News Vol. 57 2007: pp. 17-2

Maceration Before and During Fermentation: Effect on Pinotage Wine Phenolic Composition, Total Antioxidant Capacity and Objective Colour Parameters

Low-temperature maceration treatments (1, 2 and 4 days at 10 and 15°C) before fermentation and juice/skin mixing treatments (punching-down, pumping-over and rotor action every hour and every 3 hours) duringfermentation were investigated in terms of their effects on Pinotage wine phenolic composition, total antioxidant capacity (TAC) and colour over three vintages (2000 to 2002). Results for pre-fermentation maceration were notconsistent between vintages. Very few significant differences in the phenolic content, TAC and objective colour parameters were observed between the control wines and wines subjected to different pre-fermentation macerationtreatments. Pre-fermentation maceration, especially at 15°C, resulted in wines with increased vitisin A content.  Improvement of wine quality when using pre-fermentation maceration treatments at 10°C was noted previously, while no detrimental effect on the wine TAC was observed. The pumping-over treatment yielded wines with lower TAC and phenol content, as well as less favourable objective colour values, indicating that the punching-down or rotor treatment would be preferred. Although mixing at hourly intervals yielded a higher content of some phenolic compounds compared to the 3-hour interval mixing, mixing frequency did not affect the TAC of the wine. The objective colour parameters, h* and b*, were slightly lower at the higher mixing frequency in 2002 indicating a shift in the direction of a magenta hue

Changes in the Phenolic Composition and Antioxidant Activity of Pinotage, Cabernet Sauvignon, Chardonnay and Chenin blanc Wines During Bottle Ageing

The effect of bottle ageing on the antioxidant activity of Pinotage, Cabernet Sauvignon, Chardonnay and Chenin blanc wines, using the 2,2'-azino-di-(3-ethylbenzothialozine-sulphonic acid) radical cation (ABTS•+) and 2,2-diphenyl-1-picrylhydrazyl radical (DPPH0) scavenging assays, was determined. Storage at 0°C, 15°C or 30°C for a period of 12 months resulted in a significant (p ≤ 0.05) decrease in both the total antioxidant activity (TAAAnTs and TAAoPPH) and the total phenol content of the wines. The antioxidant potency of the total phenols of most of the wines, which is a ratio of antioxidant activity to the total phenol content, also decreased. The total anthocyanins in the red wines decreased significantly (p ≤ 0.05) over 12 months except for storage at 0°C, while the flavanol content of the Pinotage, Cabernet Sauvignon and Chardonnay wines increased up to nine months storage with a subsequent decrease to 12 months. The flavonol content of all the wines decreased, while only minor changes in their hydroxycinnamate content were observed during the storage period. Understanding the complexity of these reactions may provide clues for stabilising especially red wines to preserve the antioxidant activity without losing the beneficial effects of colouring and flavour development during bottle ageing

The Pelona-Pico Duarte basalts Formation, Central Hispaniola : an on-land section of Late Cretaceous volcanism related to the Caribbean large igneous province

Located in Central Hispaniola, the Pelona-Pico Duarte basalts Formation (Fm.) offers an opportunity to study the Late Cretaceous Caribbean large igneous province magmatism on land. It is composed by a ~2.5km-thick pile of massive and monotonous submarine flows of basalts, locally intruded by synvolcanic dikes and sills of dolerite. The Pelona-Pico Duarte basalts Fm. was emplaced onto Turonian-Lower Campanian island-arc volcanic and sedimentary sequences, and is overlain by Maastrichtian platformal carbonates. Two 40Ar/39Ar plateau ages indicate both extrusive and intrusive magmatic activity at least during the 79-68Ma interval (Middle Campanian to Maastrichtian), so the magmas were in part coeval with the late phases of the Caribbean large igneous province. The basalts have a restricted major-and trace-element, and isotopic, compositional variation. For a range of 47.6- 50.2wt.% SiO2, the Pelona-Pico Duarte basalts Fm. has relatively high contents in TiO2 (1.5-3.6wt.%) and Fe2O3T (10.7-13.1wt.%). On the basis of MgO contents, samples can be classified into tholeiitic basalts (20 and Zr/Nb<10) are characteristic of transitional and alkalic oceanic-island basalts. In terms of Sr-Nd isotopic composition, the samples are homogeneous and enriched relative to older Caribbean large igneous province units in Hispaniola, with (87Sr/86Sr)i ratios between 0.70330 and 0.70348 for a very restricted range of (eNd)i values between +5.0 and +5.9 (where i=70Ma). The Pelona-Pico Duarte basalts Fm. are interpreted as partial melts of a plume-related, deep enriched source, which have not been contaminated by active subduction. Mantle melt modelling indicates that both high-Mg basalts and basalts formed by mixed melts of both garnet and spinel lherzolite in variable amounts. Melts incorporated at different mantle depths, most probably in relation to the melt column processes in an upwelling plume. The Pelona-Pico Duarte basalts Fm. has significantly different values of petrogenetic tracers compared to underlying arc-related lavas, indicating a fundamental change in the mantle sources. It has geochemical affinities with the mantle domain influenced by the Late Cretaceous Caribbean plume, suggesting that enriched mantle was flowing toward the NE, to the mantle wedge region of the Caribbean island-arc, in response to rollback of the SWdirected subduction of the proto-Caribbean slab

Editorial

South Africa’s vital statistics are currently not suitable for monitoring progress towards injury and violence Sustainable Development Goal

Climatic Region and Vine Structure: Effect on Pinotage Wine Phenolic Composition, Total Antioxidant Capacity and Colour

The phenolic composition, total antioxidant capacity (TAC) and colour of Pinotage wines of the 2001, 2002 and 2003 vintages were investigated, using spectrophotometric, high-performance liquid chromatography (HPLC), free radical scavenging and objective colour analyses. Grapes were harvested from grapevines in three climatic regions ranging from cool to warm, with bush (20- and 30-cm trunk height) and trellised (30- and 60-cm trunk heights) vine treatments, on several vineyard sites in each climatic area. Climatic region had a significant effect on the content of several phenolic compounds; the concentration of anthocyanin monoglucosides, flavonols, flavan-3-ols and tartaric acid esters of hydroxycinnamic acids generally increased as the climatic region becomes cooler, while concentrations of acylated derivatives and free hydroxycinnamic acids decreased. Wines made from bush vines contained higher concentrations of flavonols, gallic acid and flavan-3-ols than those from trellised vines, but lower concentrations of some anthocyanin monoglucosides and acylated derivatives, as well as non-coloured polymers.  These trends resulted in differences in TAC and objective colour parameters, although the different vintages did not show the same trends in all cases. More vintages should therefore be investigated to clarify these effects. Wines from the cool climatic regions and from bush vines were generally darker coloured, with higher TAC than those from the warm climatic regions and bush vines, respectively. High TAC, therefore, coincided with higher colour quality. Variations in TAC were partly explained by trends for individual phenolic compounds, although unknown compounds played a major role

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