Adaptations in trunk-pelvis coordination variability in response to fatiguing exercise.

BACKGROUND: During walking, variability in how movement is coordinated between body segments from stride to stride facilitates adaptation to changing environmental or task constraints. Magnitude of this inter-segmental coordination variability is reduced in patient populations and may also decrease in response to muscle fatigue. Previously, stride-to-stride variability has been quantified with the Vector Coding (VC) method, however recent research introduced a new Ellipse Area Method (EAM) to avoid statistical artifacts associated with VC. RESEARCH QUESTION: Determine changes in trunk-pelvis coordination variability during walking turns in response to fatiguing exercise and to compare coordination variability quantified with VC to the EAM method. METHODS: 15 young adults (mean age: 23.7 (±3.2) years) performed 15 trials of a 90-degree walking turn before and after fatiguing paraspinal muscle exercise. Angular kinematics of the trunk and pelvis segments in the axial plane were quantified using three-dimensional motion capture. Stride to stride variability of axial coordination between the trunk and pelvis pre- and post-fatigue was calculated using both VC and EAM methods. Magnitudes of pre- and post-fatigue variability for VC and EAM were compared with paired t-tests and relationship between the magnitude of variability for the two methods was calculated using Pearson correlation coefficients. RESULTS: Using both analytical approaches, trunk-pelvis coordination variability decreased significantly post-fatiguing exercise across the stride cycle and within the stance phase of the turn (p < 0.034 for all comparisons). Average magnitudes of variability calculated with VC and EAM were highly correlated. Time series cross correlations pre-post fatigue ranged from 0.81 to 0.98. SIGNIFICANCE: In healthy individuals, magnitude of trunk-pelvis stride-to-stride coordination variability is reduced following fatiguing exercise but the temporal distribution of variability across the stride cycle is maintained. This finding is robust to the method used to quantify coordination variability.

Characterisation of interfacial segregation to Cu-enriched precipitates in two thermally aged reactor pressure vessel steel welds.

To understand the contribution of long term thermal ageing to Reactor Pressure Vessel (RPV) embrittlement two high Cu steel welds with different Ni contents were thermally aged for times up to 100,000 h at 330 °C and 365 °C. Microstructural characterisation using Atom Probe Tomography was performed. Thermal ageing produced a high number density of nano-scale Cu-enriched precipitates. The precipitate-matrix interfaces were enriched in Ni, Mn and Si. The characterisation of these interfaces using a double cluster search approach is the subject of this work. The interface region around thermally-induced precipitates was found to be wider in steels with higher bulk Ni contents and where precipitates had larger core radii. The effect of ageing temperature on interface width was small when comparing precipitates of equal core radius. The narrower interface width in the lower Ni steels is reflected in the composition of the interface, which has a lower Ni content than in the higher Ni material. The reduction in interfacial energy due to the segregation of Ni, Mn and Si has been calculated and shows enhanced reductions in interfacial energy with increasing precipitate size, but no obvious effect of temperature.

A comparison of the structure of solute clusters formed during thermal ageing and irradiation.

Nanometre scale clusters form in Cu-containing reactor pressure vessel (RPV) steels during neutron irradiation. These clusters have a deleterious effect on mechanical properties, which can result in embrittlement and limit the reactor operating life. Thermal ageing of RPV steels can also induce the formation of solute clusters but it is not clear how similar these are to those formed during irradiation. In this work atom probe tomography, combined with detailed structural assessments of the structure of solute clusters, is used to address this issue. A series of thermal ageing heat treatments has been performed on several high- and low-Ni RPV welds to produce 1-4 nm diameter solute clusters. The same materials have also been neutron irradiated. The results show that CuMnNiSi enriched clusters formed during thermal ageing have, on average, higher Cu contents and lower Mn, Ni and Si contents than those found in irradiation-induced clusters. The effect of increasing bulk Ni is to encourage the formation of clusters with significantly higher Ni content, slightly higher Mn and Si contents and significantly lower Cu contents. At very high doses and dose rates MnNiSi enriched clusters can form even in high-Cu welds. Despite differences in the compositions of individual clusters formed during irradiation and during thermal ageing, clusters in both exhibit similar structure. In particular, well developed clusters in both materials have Cu-enriched cores whose peripheries are enriched in Ni, Mn and, in most cases, Si.

A sensitivity analysis of the maximum separation method for the characterisation of solute clusters.

Variants of the maximum separation method have become the de-facto methodologies for the characterisation of nanometre scale clusters in atom probe tomography (APT) data obtained from dilute solid solutions. All variants rely on a number of parameters and it is well known that the precise values for these parameters strongly influence estimates of cluster size and number density. Quantitative analyses require an improved understanding of the inter-relationship between user-defined parameters, experimental parameters such as detection efficiency and the resultant parameterisation of the microstructure. A series of simulations has been performed to generate clusters with a range of compositions (50-100%) and diameters (1.5-2.5 nm) in a dilute solid solution. The data were degraded to simulate the effects of the finite detection efficiencies and positioning uncertainties associated with the ECOPoSAP and LEAP-3000X HR. An extensive analysis of each resultant dataset, using a range of values for the maximum separation parameters was then performed. Optimum values for each material condition were identified and it is shown that it is possible to characterise cluster size, number density and matrix chemistry. However, accurate estimates of cluster compositions are more difficult and absolute measurements must be treated with caution. Furthermore, it is shown that D(MAX) must increase with decreasing detection efficiency and consequently clusters of a specific size will appear slightly larger in atom probes with a lower detection efficiency.

Atom probe tomography of reactor pressure vessel steels: an analysis of data integrity.

In this work, the importance of optimising experimental conditions for the analysis of reactor pressure vessel (RPV) steels using atom probe tomography is explored. The quality of the resultant atom probe data is assessed in terms of detection efficiency, noise levels and mass resolution. It is demonstrated that artefacts can exist even when experimental conditions have been optimised. In particular, it is shown that surface diffusion of some minority species, including P and Si, to major poles prior to field evaporation can be an issue. The effects were most noticeable during laser pulsing. The impact of surface migration on the characterisation of dislocations and grain boundaries is assessed. The importance of selecting appropriate regions of the reconstructed data for subsequent re-analysis is emphasised.

Delayed presentation of ipsilateral femoral neck fractures in diaphyseal femur fractures.

Femoral neck fractures with delayed presentation following ipsilateral femoral diaphyseal fracture stabilization have been described as clandestine, attributed to missed diagnosis, or related to surgical technique. Clandestine fractures are present from time of injury but not detectable. The authors hypothesize that femoral neck fractures with delayed presentation can be clandestine, missed, or caused by surgical technique. A retrospective study and a comprehensive literature review are presented to determine the true incidence and etiology of these fractures.

Risk and protective behaviours of bisexual minority women: a qualitative analysis.

BACKGROUND: Public health messages urging women to seek health care services such as sexually transmitted diseases (STD) and cervical cancer screening or family planning services fail to address women who have sex with women (WSW). This negligence may have led to a false sense of security amongst WSW concerning sexual risk behaviour. Research has shown that WSW engaged in more high-risk sexual behaviours than heterosexual women. WSW has been identified as an important vector in the spread of STDs in all populations because of bisexuality. To prevent and reduce transmission of STDs amongst WSW, perceptions of risk for STD amongst WSW need to be understood so that effective interventions may be developed. AIM: To describe the relationship between sexual risk and protective behaviour and STD transmission amongst bisexual minority women with a history of STD. METHODS: Life history methods were used to interview 23 African-American bisexual women with a history of STD. FINDINGS: Various themes unfolded during analysis of the patient interviews, including bisexual women's perceptions of STD risk, the context of sexual relationships with women and STD prevention, screening, and treatment practices. CONCLUSIONS: The contexts of sexual relationships including multiple or concurrent partner relationships with both men and women placed these women at high risk for STD. Regardless of the type of relationship or belief it is possible to get an STD, protection was often not used. These circumstances identify an extremely high-risk population of women with need for more extensive research to identify strategies for health care interventions.

Disorders of the acromioclavicular joint.

The acromioclavicular joint is a frequent source of shoulder pain.This article reviews acromioclavicular separations and other disorders affecting the joint and its surrounding structures.

Muscle adenosine 5'-triphosphate and creatine phosphate concentrations in relation to nutritional status and sepsis in man.

1. Intramuscular concentrations of adenosine 5'-triphosphate (ATP) and creatine phosphate were measured in the vastus lateralis muscle of 28 non-septic malnourished patients and 31 septic malnourished patients. Similar measurements were made on the rectus abdominis muscle of about one-third of these patients. All results were compared with those obtained from 15 normally nourished non-septic control subjects. 2. Objective measurements of nutritional status (both anthropometric and biochemical) and sepsis were recorded in all subjects. 3. The vastus lateralis muscle of the non-septic and septic malnourished patients had intramuscular concentrations of ATP and total adenine nucleotides (TAN) that were up to 30% lower than control values, depending on the reference base used. 4. In the rectus abdominis muscle, ATP and TAN concentrations were up to 60% lower than control values, and creatine phosphate up to 47% lower, again depending on the reference base used. 5. In both muscles, the changes were more marked in those patients who were septic as well as malnourished.

Intracellular free amino acids in undernourished patients with or without sepsis.

1. Thigh muscle samples for analysis were obtained from 35 control subjects and 12 severely ill patients, of whom five had disease-induced undernutrition and seven had associated sepsis. An improvement in the Bergström technique for analysing muscle needle biopsy samples was used. 2. Muscle water, chloride and DNA were increased in both groups of ill patients, indicating an increase in the extracellular component and loss of muscle protein. 3. Falls in the concentrations of glutamine, glutamate, arginine, histidine, ornithine and lysine and rises in those of glycine, serine, asparagine, tyrosine, valine, leucine, isoleucine, phenylalanine, methionine and tryptophan were observed in the group of ill patients compared with those in the control subjects. The changes were present mainly in the patients with sepsis, significant differences between these and the undernourished ones without associated sepsis being observed in glutamine, lysine, tyrosine, valine, leucine, isoleucine, phenylalanine and methionine. The changes were either absent or slight in plasma. 4. The increased concentrations observed in six essential amino acids in the septic patients, but not in those with undernutrition, is consistent with the increased catabolic rate of sepsis. 5. However, the branched-chain amino acids, and lysine, threonine, arginine, and histidine, were present in lower concentrations than might be expected from catabolism, presumably due to utilization. It is suggested therefore that septic patients might benefit from increased proportions of these amino acids in their feeding regimen.

The effect on cholinesterase activity of storage of undiluted whole blood sampled from men exposed to o-isopropoxyphenyl methylcarbamate (OMS-33).

An observation made during an operational field trial with o-isopropoxyphenyl methylcarbamate (OMS-33) suggested that the cholinesterase in undiluted blood samples from workers exposed to that insecticide was inhibited during the storage of those samples before assay.A laboratory investigation has now shown that rapid falls of whole-blood cholinesterase activity do indeed occur during the storage of undiluted samples collected from workers at different times after exposure to OMS-33, but that no such change occurs during the same period of time in circulating blood.Several possible explanations are put forward to account for the fact that, although the carbamate persists in the circulating blood for several hours after cessation of exposure, it does not appreciably inhibit cholinesterase in vivo but only under storage conditions in vitro. The implications of this phenomenon, in so far as methods for determining cholinesterase activity in persons exposed to carbamate insecticides are concerned, are discussed; and the authors point out that, whenever storage of undiluted samples precedes the assay, the spectrophotometric method should be regarded as giving results reflecting daily fluctuations of inhibitor concentration rather than as measuring the actual whole-blood cholinesterase in the body.