Assessing the validity and sensitivity of microbial processes within a hydrodynamic model.

Eutrophication due to excess anthropogenic nutrients in waterways is a significant issue worldwide. The pressure-stressor-response of a waterway to excessive nutrient loading is reliant on numerous physical and biological factors, including hydrodynamics and microbial processing. While substantial progress has been made towards simulating these mechanisms there are limited multi-disciplinary studies that relate the physical hydrodynamics of a site with the ecological response from linked laboratory and field studies. This paper presents the development of a coupled hydrodynamic and aquatic ecosystem response model, expanded to include an integrated microbial loop, that allows the explicit representation of heterotrophic bacteria growth and dissolved organic nutrient mineralisation. A unique long-term water quality dataset at an estuary in south-eastern Australia was used to validate and assess the model's sensitivity to complex biophysical processes driving the observed water quality variability. Results indicate that explicit time-varying bacterial mineralisation rates provide a substantially improved understanding of the broader aquatic ecosystem response than assigned fixed bulk rate parameter values, which are typically derived from non-local literature. Implementation of a microbial loop at the study site indicated that the model is sensitive to the boundary conditions, in particular catchment loads, with both net transport rates and the net growth rates of heterotrophic bacteria demonstrating different responses. Under average flow conditions, a smaller net transport and reduced nutrient availability has a pronounced effect of lowering net growth rates through the applied limitation factors. During high flow conditions, freshwater inflows increased net transport and nutrient loads, which resulted in higher net growth rates. Further, temporal variability in water temperature had a compounding effect on the model's response sensitivity. This approach has broader application in other riverine systems subject to eutrophication, and in interrogating linkages in hydrodynamic and microbial mediated processes (e.g., productivity). Future studies are recommended to better understand the sensitivity of aquatic ecosystem response models to microbial net growth rate kinetics at different temperatures and from top-down predation (e.g., zooplankton grazing).

Implications of bacterial mineralisation in aquatic ecosystem response models.

Widespread wastewater pollution is a major barrier to the sustainable management of freshwater and coastal marine ecosystems worldwide. Integrated multi-disciplinary studies are necessary to improve waterway management and protect ecosystem integrity. This study used the Generalised Likelihood Uncertainty Estimation (GLUE) methodology to link microbial community ecotoxicology laboratory data to a mechanistic aquatic ecosystem response model. The generic model provided good predictive skill for major water quality constituents, including heterotrophic bacteria dynamics (r2 = 0.91). The model was validated against observed data across a gradient of effluent concentrations from community whole effluent toxicity (WET) laboratory tests. GLUE analysis revealed that a combined likelihood measure increased confidence in the predictive capability of the model. This study highlights the importance of calibrating aquatic ecosystem response models with net growth rates (i.e., sum of the growth minus loss rate parameter terms) of biological functional groups. The final calibrated net growth rate value of heterotrophic bacteria determined using the GLUE analysis was selected to be 0.58, which was significantly greater than the average literature value of -0.15. This finding demonstrated that use of literature parameter values without a good understanding of the represented processes could create misleading outputs and result in unsatisfactory conclusions. Further, fixed bulk mineralisation rate literature values are typically higher than realistically required in aquatic ecosystem response models. This indicates that explicitly including bacterial mineralisation is crucial to represent microbial ecosystem functioning more accurately. Our study suggests that improved data collection and modelling efforts in real-world management applications are needed to better address nutrients released into the natural environment. Future studies should aim to better understand the sensitivity of aquatic ecosystem response models to bacterial mineralisation rates.

Wastewater effluents cause microbial community shifts and change trophic status.

Widespread wastewater pollution is one of the greatest challenges threatening the sustainable management of rivers globally. Understanding microbial responses to gradients in environmental stressors, such as wastewater pollution, is crucial to identify thresholds of community change and to develop management strategies that protect ecosystem integrity. This study used multiple lines of empirical evidence, including a novel combination of microbial ecotoxicology methods in the laboratory and field to link pressure-stressor-response relationships. Specifically, community-based whole effluent toxicity (WET) testing and environmental genomics were integrated to determine real-world community interactions, shifts and functional change in response to wastewater pollution. Here we show that wastewater effluents above moderate (>10%) concentrations caused consistent significant shifts in bacterial community structure and function. These thresholds of community shifts were also linked to changes in the trophic state of receiving waters in terms of nutrient concentrations. Differences in the community responses along the effluent concentration gradient were primarily driven by two globally relevant bacterial indicator taxa, namely Malikia spp. (Burkholderiales) and hgcI_clade (Frankiales). Species replacement occurred above moderate effluent concentrations with abundances of Malikia spp. increasing, while abundances of hgcI_clade decreased. The responses of Malikia spp. and hgcI_clade matched gene patterns associated with globally important nitrogen cycling pathways, such as denitrification and nitrogen fixation, which linked the core individual taxa to putative function and ecosystem processes, rarely achieved in previous studies. This study has identified potential indicators of change in trophic status and the functional consequences of wastewater pollution. These findings have immediate implications for both the management of environmental stressors and protection of aquatic ecosystems.

Force coordination strategies in on-water single sculling: Are asymmetries related to better rowing performance?

Asymmetries of the rowing stroke cycle have been assessed with reference to kinematics and foot-force measures in laboratory testing environments. It remains unclear how asymmetries in propulsive kinetic measures are related to on-water rowing performance. A new approach for the evaluation of both global and local asymmetries across the entire movement was used to assess the continuous role of asymmetries and whether these change according to the level of competitive representation. Twenty-seven highly skilled female rowers (national and international competition level), rowing at 32 strokes per minute in a single scull boat, were evaluated. A symmetry index (SI) and functional data analysis (FDA) techniques were applied to a continuous difference time-series, which described fluctuating asymmetry in propulsive pin forces for each rower. Univariate ANOVAs revealed that differences in asymmetries were present as a factor of competition level for the SI and results of FDA. International athletes were more likely to utilize an asymmetry strategy with increased stroke-side (port-side) force early in the drive phase and increased bow-side (starboard) force through the second half of the drive. This was likely the result of international performers customizing their movement strategies relative to known boat mechanical offsets. The first half of the drive phase was also found to be an adaptive part of the rowing stroke cycle, suggesting asymmetries may have a functional role in successful execution of movements during the rowing stroke.

Assessment of propulsive pin force and oar angle time-series using functional data analysis in on-water rowing.

The graphical presentation of the propulsive force applied at the pin plotted relative to the horizontal angle of the oar has been used practically in on-water rowing for the qualitative assessment of skill. How the pattern is related to performance variables has not been well identified, particularly for highly trained sculling athletes. Bivariate functional principal components analysis (bfPCA) was used on force-angle data to identify the main modes of variance in curves representing twenty-seven female rowers of different competition levels (national level and international level), rowing at 32 strokes per minute in a single scull boat. Discriminant function analysis showed moderate classification of rowers using force-angle graphs across both sides of the boat, with rate of force development identified as a potentially important characteristic for international rowers. Additionally for the bow-side, spending less time in the first half of the drive phase was also identified as an important feature for international rowers. Multiple linear regression of scores from the bfPCAs showed that a more pronounced front-peaked profile was associated with a higher average boat velocity. The results of this demonstrate that different characteristics of the force-angle graph may be associated with different metrics of performance.

Common functional principal components analysis: a new approach to analyzing human movement data.

In many human movement studies angle-time series data on several groups of individuals are measured. Current methods to compare groups include comparisons of the mean value in each group or use multivariate techniques such as principal components analysis and perform tests on the principal component scores. Such methods have been useful, though discard a large amount of information. Functional data analysis (FDA) is an emerging statistical analysis technique in human movement research which treats the angle-time series data as a function rather than a series of discrete measurements. This approach retains all of the information in the data. Functional principal components analysis (FPCA) is an extension of multivariate principal components analysis which examines the variability of a sample of curves and has been used to examine differences in movement patterns of several groups of individuals. Currently the functional principal components (FPCs) for each group are either determined separately (yielding components that are group-specific), or by combining the data for all groups and determining the FPCs of the combined data (yielding components that summarize the entire data set). The group-specific FPCs contain both within and between group variation and issues arise when comparing FPCs across groups when the order of the FPCs alter in each group. The FPCs of the combined data may not adequately describe all groups of individuals and comparisons between groups typically use t-tests of the mean FPC scores in each group. When these differences are statistically non-significant it can be difficult to determine how a particular intervention is affecting movement patterns or how injured subjects differ from controls. In this paper we aim to perform FPCA in a manner allowing sensible comparisons between groups of curves. A statistical technique called common functional principal components analysis (CFPCA) is implemented. CFPCA identifies the common sources of variation evident across groups but allows the order of each component to change for a particular group. This allows for the direct comparison of components across groups. We use our method to analyze a biomechanical data set examining the mechanisms of chronic Achilles tendon injury and the functional effects of orthoses.

The effect of ultrasonically activated irrigation on reduction of Enterococcus faecalis in experimentally infected root canals.

AIM: To investigate the ability of an ultrasonically activated irrigating system to eliminate bacteria from the canal wall and dentinal tubules of extracted teeth. METHODOLOGY: One hundred and thirty roots of intact human teeth were inoculated with Enterococcus faecalis for 4 weeks. The straight roots were randomly allocated to a baseline group (n=25) or subjected to routine cleaning and shaping procedures (n=105). Two sub-groups of prepared canals were then additionally exposed either to ultrasonic irrigation with 1% sodium hypochlorite (NaOCl) for 1 min (n=35) or to 1 week of intracanal medication with calcium hydroxide [Ca(OH)(2)] (n=35). All roots were processed for light microscopy (Brown and Brenn stain) (n=28) or scanning electron microscopy (n=7). Triplicate histological sections from each of the apical, middle and coronal thirds were scored for bacterial presence using pre-defined criteria. RESULTS: Baseline bacterial penetration resulted in an average depth of tubule invasion of 151 µm. Routine canal preparation failed to eliminate bacteria consistently from either the canal wall or within tubules. Ultrasonic irrigation and medication with Ca(OH)(2) consistently eliminated bacteria from the canal wall (P<0.001) compared with baseline and routine treatment, and more frequently from dentinal tubules than routine canal preparation alone (P<0.01). Ultrasonic irrigation was as effective in bacterial reduction as 1 week of intracanal medication with Ca(OH)(2), but neither led to complete bacterial elimination in all roots. CONCLUSIONS: Ultrasonically activated irrigation for 1 min with 1% NaOCl after canal preparation in straight root canals is potentially an effective supplementary step in microbial control.

Functional data analysis of joint coordination in the development of vertical jump performance.

Mastery of complex motor skills requires effective development of inter-segment coordination patterns. These coordination patterns can be described and quantified using various methods, including descriptive angle-angle diagrams, conjugate cross-correlations, vector coding, normalized root mean squared error techniques and, as in this study, functional data analysis procedures. Lower limb kinematic data were obtained for 49 children performing the vertical jump. Participants were assigned to developmental stages using the criteria of Gallahue and Ozmun . Inter-segment joint coordination data consisting of pairs of joint angle-time data were smoothed using B-splines and the resulting bivariate functions were analysed using functional principal component analysis and stepwise discriminant analysis. The results of the analysis showed that the knee-hip joint coordination pattern was most effective at discriminating between developmental stages. The results provide support for the application of functional data analysis techniques in the analysis of joint coordination or time series type data.

Diel variation in egg-laying by the freshwater fish louse Argulus foliaceus (Crustacea: Branchiura).

Removal of deposited eggs could be a useful control strategy for the damaging fish ectoparasite Argulus foliaceus, but focused control requires knowledge of egg-laying patterns. Here, we investigated diel changes in the egg-laying behaviour of a natural population of A. foliaceus. Data were collected from 17-28 May 2004. Days were divided into 3 time periods: 06:00-14:00, 14:00-22:00 and 22:00-06:00 h. Significantly more egg clutches were laid from 06:00-14:00 h than during the other 2 time periods, which were not significantly different from each other. Significantly more egg clutches per hour were laid during hours of daylight as compared to hours of darkness. Significantly more egg clutches were laid in the top 1 m of the water column than at the bottom, and this was consistent throughout all 3 time periods. It is suggested that the increase in egg-laying activity during daylight hours may be due to a higher motivation to search for hosts during the night and an increased ability to locate silhouetted egg-laying sites during the day. These data can provide information useful for egg removal and control strategies.

Seasonal and vertical patterns of egg-laying by the freshwater fish louse Argulus foliaceus (Crustacea: Branchiura).

Argulus foliaceus is a damaging fish ectoparasite for which new control measures are being developed based on egg-removal. In an attempt to develop further understanding of seasonal and vertical egg-laying patterns in this parasite, egg-laying activity was monitored over the period 14 April to 17 November 2003 in 2 rainbow trout Oncorhynchus mykiss fisheries in Northern Ireland, UK. At Site 1, egg-laying was continuous from 21 April to 17 November, when water temperature was above 8 to 10 degrees C. At Site 2, egg-laying was continuous from 4 June to 29 October. In the early months of the season, egg-laying was recorded mainly within the top 1 m of the water column; however, a significant shift to deep water egg-laying was recorded between 7 July and 17 November at Site 1 and between 20 August and 29 October at Site 2. Egg clutches were preferentially laid at depths of up to 8.5 m during this time (Site 2), a feature of egg-laying hitherto unappreciated. Temperature and dissolved oxygen did not differ significantly among depths, but there was an increase in water clarity over time. However, the precise environmental triggers for deep water egg-laying are still unclear. These new insights into the reproductive behaviour of this species will be useful in developing control methods based on egg-removal.

A simple way to model wires used in ring fixators: analysis of the wire stiffness effect on overall fixator stiffness.

The Ilizarov fixator has become widely used in the treatment of complex trauma and deformity correction in the United Kingdom over the last few decades. As such, it has been widely researched. Within this fixator, the characteristic fine wires are the weakest and most flexible component. The wires allow interfragmentary micromotion, which is believed to be beneficial to bone healing. In this paper, a novel and simple numerical model of the stiffness and deflection of the wires when the fixator is subject to axial and torsional loading is presented. A range of wire lengths and pretensions are analysed, and the results compared to the findings of other researchers, with generally good agreement. This indicates that fixator stiffness can be determined simply and without recourse to sophisticated finite element analyses or extensive physical testing. In addition, the model is used to predict the contribution of the wires to the overall stiffness of the fixator.

The application of force-sensing resistor sensors for measuring forces developed by the human hand.

Most attempts to measure forces developed by the human hand have been implemented by placing force sensors on the object of interaction. Other researchers have placed sensors just on the subject's fingertips. In this paper, a system is described that measures forces over the entire hand using thin-film sensors and associated electronics. This system was developed by the authors and is able to obtain force readings from up to 60 thin-film sensors at rates of up to 400 samples/s per sensor. The sensors can be placed anywhere on the palm and/or fingers of the hand. The sensor readings, together with a video stream containing information about hand posture, are logged into a portable computer using a multiplexer, analogue-to-digital converter and software developed for the purpose. The system has been successfully used to measure forces involved in a range of everyday tasks such as driving a vehicle, lifting saucepans and hitting a golf ball. In the latter case, results are compared with those from an instrumented golf club. Future applications include the assessment of hand strength following disease, trauma or surgery, and to enable quantitative ergonomic investigations.

Dexamethasone and retinoic acid differentially regulate growth and differentiation in an immortalised human clonal bone marrow stromal cell line with osteoblastic characteristics.

Clonogenic immortalised human pre-osteoblastic cell lines provide useful species-specific experimental tools for the study of the regulation of osteoblastic proliferation and differentiation. Steroid hormones are major regulators of bone formation. Although much is known about the effects of dexamethasone on osteoblastic growth and differentiation in vitro, there is less information on the effects of trans-retinoic acid (RA), particularly in human cultures. We have established a clonal adult human cell line (C1) derived from a bone marrow aspirate. The cell line appeared to be bi-potential. The cells were able to differentiate into an adipocytic phenotype under appropriate culture conditions. When grown in osteogenic medium, the cells expressed alkaline phosphatase (ALP) and osteocalcin mRNA. The C1 cells also expressed several other osteoblastic markers such as collagen type 1 (COL 1), PTH/PTH-rp receptor constitutively. Transcripts for the osteoblast transcription factor Cbfa1 was also detected under basal conditions. In addition treatment with 1,25(OH)(2)D(3) (10(-7)M) led to a marked increase in osteocalcin mRNA expression suggesting that this cell line represents a pre-osteoblastic population. We compared the effects of Dex and RA on osteoblastic function. For the assessment of PTH/PTH-rp receptor, osteocalcin and Cbfa1 mRNA expression and PTH-stimulated adenylate cyclase responsiveness, the cells were grown in the presence of Dex and RA and harvested on Days 1, 3, 7 and 14. RA (10(-7)M) had a mitogenic effect on the C1 cells. In contrast, Dex (10(-7)M) inhibited proliferation. A similar effect was observed with primary human bone marrow stromal cultures. Both Dex and RA inhibited COL 1 synthesis and decreased COL1 mRNA. Dex stimulated ALP activity and increased ALP mRNA expression whilst RA had an inhibitory effect. Dex treatment led to an increase in PTH/PTH-rp receptor mRNA and PTH-induced cAMP accumulation with a peak response at 24 h and this effect was sustained for up to 14 days. In contrast, long-term culture with RA resulted in a reduction in the cAMP response to PTH (Days 7 and 14) with no effect on PTH/PTH-rp receptor mRNA expression. Osteocalcin and Cbfa1 mRNA expression did not alter in the presence of Dex and RA at these time points. This study shows that Dex and RA have differential effects on the expression of the phenotypic markers and genes associated with osteoblast maturation. This homogeneous cell line can therefore be used further to elucidate the cellular and molecular mechanisms of action of Dex and RA at the different developmental stages of human osteoblastic differentiation. This cell line may thus provide a useful species-specific in vitro model for the evaluation of key genes and signalling molecules involved in osteogenesis. This would be of help in the design of 'in vivo' studies.

Motor development and gender effects on stretch-shortening cycle performance.

A substantial part of human movement such as jumping, hopping, leaping and other bounding movements are improved by making a counter-movement. These activities are often described as stretch shortening cycle (SSC) movements. The aim of this study was to determine whether the SSC affects performance in vertical jump in children to the same extent as it does in adults. Comparisons were made between counter-movement jump (CMJ) and squat jump (SJ) performance in children and adults. The ratio of take-off velocity between jumps was used to measure performance of the SSC. Two groups of subjects comprising of 22 adults and 20 children performed three CMJ's and three SJ's from a force platform. Impulse, take-off velocity and power were obtained by numerical integration of the force n time traces. Performance was calculated from the velocity at take off. Both groups jumped significantly higher in the CMJ but there was a higher degree of variability in the performance of the children. The results indicated that children could utilise a SSC to enhance jumping performance. Variability in the take-off velocities in children, particularly in the SJ suggests the children performed this jump non-optimally.

A moment-based technique for the automatic spatial alignment of plantar pressure data.

Plantar pressure measurements have many potential clinical applications in the field of orthopaedics. However, the only current routine clinical application of pedobarography is for the identification of high pressure zones in diabetic patients with neuropathy who are at risk from foot ulceration. For pedobarography to become a routine clinical tool in orthopaedics, a thorough knowledge of normal plantar pressure distributions would be required. To date, no large scale studies to define population norms have been conducted, probably because of the high cost associated with analysing large quantities of plantar pressure data. Plantar pressure distributions display a high step-to-step variation and, therefore, it is necessary to conduct multiple trials. Comparison between these trials is difficult, somewhat subjective, and slow, because it must be conducted manually. The present authors have developed a technique to align automatically the spatial components of a series of datasets. The technique then allows predefined parameters to be automatically extracted from the data, hence greatly reducing analysis time. The authors believe that not only does the technique make large scale studies economically viable but that it could also form the basis for expert systems for the diagnosis of foot pathologies and the prescription of orthoses.

Schemes for the identification of tissue types and boundaries at the tool point for surgical needles.

Precise control of automated invasive surgical tools requires real-time identification of tissue types and their deformation. At the focus of this paper is the epidural puncture, for which it is shown that the tissue type and deformation can respectively be determined from laser-based spectroscopy and the change in force required to push the needle through the various tissues. Studies have shown that physiological variations from one patient to another are too great to allow absolute values to be reliably used to indicate the position of the needle tip. However, the pattern of force variation during penetration is shown to be similar between specimens. Interpretation of this information in conjunction with spectroscopic techniques can be used to discriminate between tissues and tissue structure at the needle tip. This paper describes results from an investigation on automatic techniques for interpreting the type and deformation of tissues under tool action.

The yielding of tensioned fine wires in the Ilizarov frame.

The Ilizarov frame uses tensioned fine wires to support bone fragments. The objective of this study was to determine whether these wires deformed plastically under functional load bearing and to determine the significance of such deformation on the long-term performance of frames used for treating lower limb conditions. The mechanical characteristics of the wires were determined by means of destructive tensile tests and used in the construction of a series of finite element models replicating typical frame configurations. Each model was then subjected to a single load cycle representing a single step and the residual displacement (i.e. plastic deformation) was determined. In each case a residual displacement of between 0.26 and 0.42 mm was observed giving a corresponding reduction in wire tension of between 8.3 and 32.8 per cent. These reductions in wire tension reduce the frame's overall stiffness and so compromise its ability to inhibit high-amplitude axial and shear motions at the fracture site which are deleterious to the healing outcome.

Hospitals in England: impact of the 1990 National Health Service reforms.

OBJECTIVES: This article aims to describe recent changes in English hospitals, with particular reference to the impact of the National Health Service (NHS) and Community Care Act of 1990. METHODS: Significant policies that have affected the functioning of the hospital sector of the British NHS are reviewed. Data from the NHS Department of Health are used to describe trends in utilization. RESULTS: The NHS and Community Care Act of 1990 radically changed the financial and organizational framework within which hospitals operate. By creating separate purchasing organizations, the act opened the way for competition between hospitals. In practice, such competition has been very limited. Central directives aimed at reducing waiting times for nonurgent admissions, as well as at raising the volume of work done relative to the finances available have been more significant influences. These changes, combined with rising numbers of emergency admissions, have put the physical and human resources of English hospitals under intense pressure. Admissions have risen, lengths of stay have fallen across all age groups, and ambulatory care has grown rapidly. CONCLUSIONS: There is little consensus on the future direction regarding the role and structure of acute-care hospitals. There is evidence, though, that improvements in the process and outcomes of care are possible within the current financial and organizational framework of the hospital sector.

Postural instability in diabetic neuropathic patients at risk of foot ulceration.

Diabetic peripheral neuropathy is believed to cause postural instability due to abnormal proprioception. We assessed body sway in four groups, each of 20 subjects, matched for age, sex, and BMI: non-diabetic controls, non-neuropathic diabetic controls, subjects with diabetic neuropathy and no history of foot ulceration, and subjects with diabetic neuropathy and a history of foot ulceration. Postural sway was assessed on a Kistler force plate using the Romberg test, measuring the standard deviation of the centre of pressure in both sagittal (antero-posterior movement) and frontal (side to side movement) planes with eyes open and closed. The Romberg test results were log transformed and then analysed using analysis of variance followed by Newman-Keuls test. There was no significant difference in body sway between the two control groups and the first group of subjects with diabetic neuropathy. However, in patients with a history of ulceration, values were significantly higher (p < 0.05) compared to all other groups in both planes and conditions studied. These results are suggestive of a relationship between impaired body sway control and foot ulceration. Postural instability may have clinical significance and increase the risk of minor trauma and ulceration in patients with diabetic neuropathy.

Simulation of resistance forces acting on surgical needles.

High precision in the manual control of needles and biopsy probes in medical treatment requires high skill and dexterity levels. In anaesthesia, force sensation is an important feedback mechanism, and the practitioner needs to refresh or develop skills to improve on the interpretation of needle progress towards the target site. This paper describes an experimental tactile force simulator for uniaxial needle action for which the force resisting progress of the needle is derived from measured data. As an example, the approach taken to develop the simulation of the insertion of epidural needles is described. Adaptation to other procedures would be possible by adopting new reference models based on appropriate measured force data.