Video measurement of linear displacement along an oblique line using the cross-ratio

The purpose of this study was to rediscover the cross-ratio and assess its effectiveness for measuring linear displacement when the image plane is not parallel to the object plane. In the laboratory a fixed, 4m object length was reconstructed with a mean absolute error of 2.6mm (s.d. = 1.6mm, maximum = 4.9mm). In the field, two cameras filmed a fixed, 8m object length with a mean absolute error of 13mm (s.d. = 5mm, maximum = 20mm). The method is very accessible to non-specialists in projective geometry and the results are both valid and reliable

VIDEO MEASUREMENT OF LINEAR DISPLACEMENT ALONG AN OBLIQUE LINE USING THE CROSS-RATIO

The purpose of this study was to rediscover the cross-ratio and assess its effectiveness for measuring linear displacement when the image plane is not parallel to the object plane. In the laboratory a fixed, 4m object length was reconstructed with a mean absolute error of 2.6mm (s.d. = 1.6mm, maximum = 4.9mm). In the field, two cameras filmed a fixed, 8m object length with a mean absolute error of 13mm (s.d. = 5mm, maximum = 20mm). The method is very accessible to non-specialists in projective geometry and the results are both valid and reliable

To boldly go:an occam-π mission to engineer emergence

Future systems will be too complex to design and implement explicitly. Instead, we will have to learn to engineer complex behaviours indirectly: through the discovery and application of local rules of behaviour, applied to simple process components, from which desired behaviours predictably emerge through dynamic interactions between massive numbers of instances. This paper describes a process-oriented architecture for fine-grained concurrent systems that enables experiments with such indirect engineering. Examples are presented showing the differing complex behaviours that can arise from minor (non-linear) adjustments to low-level parameters, the difficulties in suppressing the emergence of unwanted (bad) behaviour, the unexpected relationships between apparently unrelated physical phenomena (shown up by their separate emergence from the same primordial process swamp) and the ability to explore and engineer completely new physics (such as force fields) by their emergence from low-level process interactions whose mechanisms can only be imagined, but not built, at the current time

Muscle activation patterns in shoulder impingement patients

Introduction: Shoulder impingement is one of the most common presentations of shoulder joint problems 1. It appears to be caused by a reduction in the sub-acromial space as the humerus abducts between 60o -120o – the 'painful arc'. Structures between the humeral head and the acromion are thus pinched causing pain and further pathology 2. Shoulder muscle activity can influence this joint space but it is unclear whether this is a cause or effect in impingement patients. This study aimed to observe muscle activation patterns in normal and impingement shoulder patients and determine if there were any significant differences. Method: 19 adult subjects were asked to perform shoulder abduction in their symptomatic arm and non-symptomatic. 10 of these subjects (age 47.9 ± 11.2) were screened for shoulder impingement, and 9 subjects (age 38.9 ± 14.3) had no history of shoulder pathology. Surface EMG was used to collect data for 6 shoulder muscles (Upper, middle and lower trapezius, serratus anterior, infraspinatus, middle deltoids) which was then filtered and fully rectified. Subjects performed 3 smooth unilateral abduction movements at a cadence of 16 beats of a metronome set at 60bpm, and the mean of their results was recorded. T-tests were used to indicate any statistical significance in the data sets. Significance was set at P<0.05. Results: There was a significant difference in muscle activation with serratus anterior in particular showing a very low level of activation throughout the range when compared to normal shoulder activation patterns (<30%). Middle deltoid recruitment was significantly reduced between 60-90o in the impingement group (30:58%).Trends were noted in other muscles with upper trapezius and infraspinatus activating more rapidly and erratically (63:25%; 60:27% respectively), and lower trapezius with less recruitment (13:30%) in the patient group, although these did not quite reach significance. Conclusion: There appears to be some interesting alterations in muscle recruitment patterns in impingement shoulder patients when compared against their own unaffected shoulders and the control group. In particular changes in scapula control (serratus anterior and trapezius) and lateral rotation (infraspinatus), which have direct influence on the sub-acromial space, should be noted. It is still not clear whether these alterations are causative or reactionary, but this finding gives a clear indication to the importance of addressing muscle reeducation as part of a rehabilitation programme in shoulder impingement patients

Low-stakes, VLE intensive, formative approach to maths teaching as a pedagogic strategy for improving assessment outcomes

Functional numeracy skills in the UK workforce have been an issue for at least 20 years and are of mounting concern due to the increasing use of technology in the workplace and the need for mathematical problem solving skills. Surveys reveal anxiety related to maths (MA) has a negative impact on Higher Education (HE) subject choices and subsequent career options. This at a time when Science, Technology, Engineering and Mathematics (STEM) subjects, requiring maths and data handling skills, are in high demand globally.This case study relates the journey from discovering the need for maths support in science students to the use of low-stakes, VLE intensive, formative maths support as a means of overcoming MA and improving student outcomes

Perceptual, mechanical and electromyographic responses to different relative loads in the parallel squat

The effectiveness of the OMNI-RES (0-10) and the electromyographic signal for monitoring changes in the movement velocity was examined during a set to muscular failure using different percentages of one repetition maximum (1RM) in the parallel squat exercise (PSQ). Twelve males (26.3 ± 5.8 years) were evaluated on eight separate days with 48 hours of rest between sessions. After determining the 1RM value, participants underwent seven tests until achieving muscular failure with the following percentage ranges: 30 to 90%. An optical rotary encoder measured mean accelerative velocity (MAV) and the OMNI-RES (0-10) scale was used to express the Rating of Perceived Exertion (RPE) after every repetition of each set. Additionally, the normalized root mean square (RMS) signal of the surface electromyography (N-EMG) was calculated for the vastus medialis muscle. The RPE expressed after the first repetition and when the maximum value of MAV was achieved along the sets was lower (p 0.8) than the RPE that corresponded to a 10% drop in MAV and at failure. Additionally, the initial RPE was useful to distinguish different loading zones by anchoring the OMNI-RES value to the magnitude of the relative load (<60%, 60 to <70% or ≤ 70% 1RM). Similar patterns were observed using the N-EMG. In conclusion, apart from differentiating between relative loads during a set to failure in the PSQ, the RPE and the N-EMG can both reflect changes associated with the initial, maximal, 10% drop in movement velocity and the muscular failure

Does whole body vibration have clinically significant neurophysiological and neurovascular implications?

Whole body vibration has received much attention as an innovative approach to exercise, leading to constantly increasing attention fro m the scientific community. Previous research considering occupational vibration has illustrated the risks associated with high levels of exposure to vibration; however during vibration exercise the exposure duration is much shorter and therefore the potential complications must be reconsidered. This review brings together research from various aspects of occupational vibration, clinical research and vibration exercise to address issues within the context of health and safety with a particular focus on neurophysiological and neurovascular responses. The results indicate that peripheral nerve and blood vessels are exposed to risks such as compression, shear stress and altered function as a response to vibration. However, correct planning and implementation of exercise protocols should effectively control these risks. By summarising the areas that have received attention an overview of potential complications will be achieved; with an understanding of which factors prevent participation and those that simply require an amended approach to vibration exercise

Modelling the distribution and abundance of several demersal fish species on the Agulhas Bank, South Africa

The Agulhas Bank supports a speciose fish community, many of which are commercially important. Despite substantial research being conducted on aspects of their biology spatial aspects of their distribution and abundance in relation to environment parameters has been ignored. This study, therefore, addressed aspects related to the distribution and abundance of representative species on the Agulhas Bank within a Geographic Information System (GIS). Four candidate species were chosen due to their importance either in numbers or unit mass to the South African demersal trawl fishery. The species also shared morphological and taxonomic similarities. The candidate species chosen were the two Cape hake species, shallow-water hake Meluccius capensis, and deep-water hake Merluccius paradoxus, and the two pleuronectiform species being Agulhas sole Austroglossus pectoralis and redspotted tonguesole Cynoglossus zanzibarensis. The use of a GIS was appropriate and allowed for hidden spatial patterns be exposed and illustrated visually, while also facilitating the quantification of the relationships between distribution/abundance and certain environmental predictors using statistical methods The Department of Marine and Coastal Management, Cape Town, supplied biological data in the form of length frequency and biomass information from spring (AprillMay) and autumn (September/October) cruises conducted between 1986 and 1993 on the R. V. Africana. The Council for National Geoscience, Cape Town, supplied sediment data for the entire southern African coastline. Initial exploratory data analysis highlighted potential relationships between environmental variables and abundance for each specie's life-history stanzas. Variations in spatial distribution were found to be significantly different between each life-history stanzas within species. Fish density as a function of the additive effects of the various environmental parameters, including temperature, depth and sediment type, was assessed using a Poisson Generalized Additive Model (GAM), while distribution was analysed with a logistic GAM. A predictive logistic model was then created, taking into consideration the importance of the predictor variables for each species, allowing for predictive estimates to be made for each species by inputting environmental information within the study area. The importance of certain environmental variables influencing distribution and abundance were noted. General patterns indicated that sediment was the most important to both the distribution and abundance of the two pleuronectiform species and juvenile life-history stanzas, while the adult gadoids' distribution and abundance appeared to be depth dependent