Bio-inspired sensing and actuating architectures for feedback control of civil structures

Civil structures, such as buildings and bridges, are constantly at risk of failure due to external environmental loads, such as earthquakes or strong winds. To minimize the effects of these loads, active feedback control systems have been proposed but such systems still face numerous challenges which impede their widespread adoption. In order to overcome many of these challenges, inspiration can be drawn from the signal processing and actuating techniques employed by the biological central nervous system to develop a bio-inspired control algorithm. In this study the front-end, signal processing techniques employed by biological sensory systems, and in particular the mammalian auditory system, are drawn upon in order to alleviate computations at the actuation node. This results in a simplistic control law that is a weighted combination of input information about the structure's response such that F   =   WN , where F is the applied control force, W is a pre-determined weighting matrix, and N is a deconstructed representation of the structural response to the applied excitation. There is no empirical solution for deriving an optimal weighting matrix, W , and in this study numerous methods are explored in order to determine values for this matrix that produce the most effective control. These methods include particle swarm optimization, artificial neural networks, and optimal control theory. The various weighting matrices are integrated into the proposed bio-inspired control algorithm and applied in simulation to a five story benchmark structure. These methods are also compared to a traditional linear quadratic regulator (LQR) to gain insight into the overall performance of the bio-inspired control algorithm. Of the three training techniques, the particle swarm optimization technique offers the most effective control which is comparable in performance to the traditional LQR.

The prediction of endurance performance from work rates at fixed blood lactate concentrations is a mathematical not a physiological phenomenon - a novel hypothesis

.

Non-thermal atmospheric pressure plasma etching of F:SnO2 for thin film photovoltaics

Thin film based photovoltaic systems offer significant advantage over wafer based technologies enabling the use of low cost, large area substrates such as glass, greatly facilitating the construction and integration of large modules. The viability of such systems has advanced in recent years, with researchers striving to optimise performance through the development of materials and cell design. One way to improve efficiency is to texture the interface between the TCO and the absorber layer to maximise scattering over the appropriate wavelength range, with nanometre scale features such as pyramids being reported as giving high scatter. These textures may be achieved by advanced growth processes, such as CVD, post growth etching or a combination of both. In this work, textured F:SnO2 films produced by APCVD were favourably modified using a remote, non thermal, atmospheric plasma to activate a selective dry etch process resulting in significantly enhanced topography. Uniform treatment of the samples was achieved by translation of the samples below the plasma head. Advantages of this approach, compared to competitive technologies such as wet chemical processes, are the relatively low power consumption and ease of scalability and retroprocess integration. The modified structures were studied using AFM, SEM and EDAX, with the observed topography controlled by process variables. Optical properties were assessed along with Hall measurements.

Analysing recurrent events in exercise science and sports medicine

Episodic or recurrent events are a class of data that is frequently reported in health sciences research. The purpose of this paper is to highlight the prevalence of published reports, especially within the South African context, that have used inappropriate statistical techniques when dealing with episodic events and to urge the use of appropriate univariate and multivariate techniques.

Effect of body mass and physical activity volume and intensity on pedometry-measured activity energy expenditure in rural black South Africans in the Limpopo Province

Objectives. We developed a novel approach to investigate patterns of pedometry-measured total weekly activity energy expenditure (EEAct) in rural black South Africans in the Limpopo Province. Design. We analysed 7-day pedometry data in 775 subjects (female: N=508; male: N=267). Variance components models for EEAct were used to estimate the variance explained by body mass (BM), total weekly steps (volume) and estimated intensity (kcal. kg-1.step-1). Univariate General Linear Models, adjusting for age, BM and physical activity (PA) volume, were used to determine if EEAct was primarily affected by volume or intensity. Results. BM (13.1%), PA intensity (24.4%) and PA volume (56.9%) explained 94.4% of the variance in EEAct. Adjusted EEAct did not differ between sexes (78 kcal.week-1, p =0.2552). There were no significant differences across activity categories (sedentary to very active) for adjusted EEAct (62 - 287 kcal.week-1, p>0.1). Adjusted EEAct for 6 - 7 days of compliance (≥10 000 steps.day-1) differed significantly from 1 - 2 days of compliance (266 - 419 kcal.week-1, p<0.04). Obese (body mass index ≥30 kg.m-2) and normal weight (body mass index 18.5 - 24.9 kg.m-2) women did not differ significantly across activity categories for EEAct (200 - 592 kcal.week-1, p>0.30). Conclusions. We have highlighted an intensity effect for days of compliance and at very active ambulatory levels (≥12 500 steps. day-1). A volume effect appeared to dominate between sexes, across activity categories and weight-by-activity categories. It is important that post hoc statistical adjustments be made for body mass and PA volume when comparing EEAct across groups.

Monitor placement, sources of variance and reliability of free-living physical activity: a pilot investigation

No Abstract.

Pedometer step counting in South Africa: tools or trinkets?

Objectives. This study addressed (i) the accuracy of measuring ambulatory signals and (ii) the susceptibility to nonambulatory signals, of the Discovery Vitality Pedometer (VT) and the Kellogg's Special K Step Counter (KL) compared with three research-grade pedometers (DW: Yamax DigiWalker SW-401, MTI: MTI Actigraph AM-7164-2.2 , NL: New Lifestyles NL 2000). Design. One hundred instruments (20 instruments/brand) were tested at five level walking speeds on a motorised treadmill (3.24, 4.02, 4.80, 5.64, 6.42 km.hr-1) and during motor vehicle travel on tarred roads (62.9 km). Results. The KL was highly variable across all speeds, while the VT tended to be variable at the lowest speed. The DW, NL and VT significantly underestimated steps below 4.80km.hr-1 (41 - 94%, p < 0.02) but accuracy improved at speeds ≥ 4.80 km.hr-1 (98 - 102%). The KL displayed the highest variability (60% inter-instrument variance) followed by the VT (10% inter-instrument variance). The research-grade pedometers were the least variable (0 - 1% inter-instrument variance). At 4.80 km.hr-1, all research- grade pedometers measured within a 10% margin of error compared with the 90% of VT units and 42% of KL units. The VT was significantly more resistant to nonambulatory signals than the DW (p < 0.01). The KL was the most variable in its response to non-ambulatory signals while the NL was the most consistent. The MTI detected the most non-ambulatory signals (p < 0.05). Conclusions. The KL should not be used as a promotional pedometer. The VT achieved the minimum standards required of a promotional pedometer. Further testing is required for longevity, and performance under free-living conditions. South African Journal of Sports Medicine Vol. 18 (3) 2006: pp. 67-78

Sources of variance and reliability of objectively monitored physical activity in rural and urban Northern Sotho-speaking blacks

Objectives. We investigated the sources of variance and reliability in an objective measure of physical activity for a 14- hour and 4-day monitoring period. Design. A convenience sample of rural (N=31) and urban (N=30) adult, Northern Sotho-speaking blacks was recruited. Physical activity was assessed for 8 consecutive days using a uni-axial accelerometer. Physical activity indices were total counts, average counts, inactivity (

Sources of variance and reliability of objectively monitored physical activity in rural and urban Northern Sotho-speaking blacks

Objectives. We investigated the sources of variance and reliability in an objective measure of physical activity for a 14- hour and 4-day monitoring period. Design. A convenience sample of rural (N=31) and urban (N=30) adult, Northern Sotho-speaking blacks was recruited. Physical activity was assessed for 8 consecutive days using a uni-axial accelerometer. Physical activity indices were total counts, average counts, inactivity (

Pedometer step counting in South Africa: tools or trinkets?

Objectives. This study addressed (i) the accuracy of measuring ambulatory signals and (ii) the susceptibility to nonambulatory signals, of the Discovery Vitality Pedometer (VT) and the Kellogg's Special K Step Counter (KL) compared with three research-grade pedometers (DW: Yamax DigiWalker SW-401, MTI: MTI Actigraph AM-7164-2.2 , NL: New Lifestyles NL 2000). Design. One hundred instruments (20 instruments/brand) were tested at five level walking speeds on a motorised treadmill (3.24, 4.02, 4.80, 5.64, 6.42 km.hr-1) and during motor vehicle travel on tarred roads (62.9 km). Results. The KL was highly variable across all speeds, while the VT tended to be variable at the lowest speed. The DW, NL and VT significantly underestimated steps below 4.80km.hr-1 (41 - 94%, p < 0.02) but accuracy improved at speeds ≥ 4.80 km.hr-1 (98 - 102%). The KL displayed the highest variability (60% inter-instrument variance) followed by the VT (10% inter-instrument variance). The research-grade pedometers were the least variable (0 - 1% inter-instrument variance). At 4.80 km.hr-1, all research- grade pedometers measured within a 10% margin of error compared with the 90% of VT units and 42% of KL units. The VT was significantly more resistant to nonambulatory signals than the DW (p < 0.01). The KL was the most variable in its response to non-ambulatory signals while the NL was the most consistent. The MTI detected the most non-ambulatory signals (p < 0.05). Conclusions. The KL should not be used as a promotional pedometer. The VT achieved the minimum standards required of a promotional pedometer. Further testing is required for longevity, and performance under free-living conditions. South African Journal of Sports Medicine Vol. 18 (3) 2006: pp. 67-78

Quantitative electroencephalographic correlates of psychosis in Alzheimer disease

OBJECTIVE

We hypothesized that the distinctive neurobiology of Alzheimer disease (AD) with psychosis would be reflected in more severe abnormalities in frontal and temporal regions on quantitative electroencephalography (QEEG).

BACKGROUND

Patients with AD and psychosis have more rapid cognitive decline and greater pathologic involvement of frontal and temporal cortex than AD patients without psychotic features.

METHOD

We evaluated brain function using QEEG in a group of 44 patients who had a diagnosis of probable or possible AD. All patients were administered the Mini-Mental State Examination and the Neuropsychiatric Inventory to assess psychiatric symptoms, including the presence of hallucinations and delusions. Absolute and relative power in patients with and without psychosis were compared to determine if there were regional or global QEEG differences in these two groups.

RESULTS

Patients with psychosis showed greater overall absolute and relative delta power but no regional predominance of slowing compared with those without psychosis. Those with psychosis had a concomitant decrease in relative alpha power. These differences remained after adjustment for different dementia severity in the two groups.

CONCLUSIONS

This finding suggests more severe brain dysfunction in patients with psychosis than in those with similar levels of cognitive impairment but without psychosis. The QEEG abnormalities were not regionally specific and involved all areas assessed.

Assessment of the efficacy, safety and quality of gentamicin use in Aberdeen Royal Infirmary

Fifty-five patients who received od gentamicin were studied. The protocol for od gentamicin was followed in 23/55 (48%). Cure rates were 22/23 (96%) when the protocol was followed and 24/32 (75%) when not followed (P = 0.06). Toxicity was more common in those in whom the protocol was not followed (9/32; 28%) than in those in whom it was followed (1/23; 4%) (P< 0.05). The number needed to treat with the protocol to produce one additional cure was 4.84 (95% CI 2.64 to 28.66) and the number needed to treat to prevent one case of toxicity was 3.61 (95% CI 2.16 to 10.99).

Effect of seizures on hippocampal peptidergic neurons

Results from animal studies and from human tissue removed from epileptics show that certain subgroups of hippocampal neurons are more vulnerable to seizure activity than others. It is possible that neurons which contain calcium-binding proteins, such as parvalbumin, may be protected from the high calcium overload that results from seizure activity. In the present study, seizures were induced by an injection of tetanus toxin into the rat hippocampus. A morphological and quantitative analysis was made of the parvalbumin-containing neurons and of those which co-localized somatostatin and neuropeptide Y. At 2 weeks there was a generalized increase in immunoreactivity in both groups of neurons. From 1 month through to 3 months after injection, the up-regulation in immunoreactivity was sustained in the surviving hilar neurons which co-localized somatostatin and neuropeptide Y but there was a marked reduction in immunoreactivity of the parvalbumin neurons. Although there was no evidence for a loss of parvalbumin neurons there was a small and significant reduction in the number of somatostatin + neuropeptide Y double-labelled neurons in the contralateral hilus at 3 and 4 months after a tetanus injection. The vulnerability of the somatostatin + neuropeptide Y double-labelled hilar neurons but not of the parvalbumin-containing, presumed, basket cells are considered in terms of their connectivity.

Influence of gravity and body position on normal oropharyngeal swallowing

The influence of gravity, if any, on pharyngeal bolus transport is unknown. The aim of the present study was to evaluate the effect of gravity and body position on the radiological and manometric events during the normal oropharyngeal swallow. In eight healthy male volunteers, we performed simultaneous videoradiography and manometry, using a manometry catheter incorporating a perfused sleeve measuring upper esophageal sphincter pressure and three solid-state transducers recording pharyngeal pressures. Swallows of 5 and 10 ml of barium were performed in three different body positions: upright, horizontal, and 30 degrees head down (inverted). Hypopharyngeal intrabolus pressure increased significantly in the horizontal and inverted positions compared with upright, P = 0.0001. This resulted in increased maximal sphincter diameters during bolus flow (P = 0.0001) and shorter duration of sphincter opening (P = 0.03). As a result, transsphincteric flow increased in the horizontal and inverted positions, P = 0.04. Total swallowing duration, oral and pharyngeal transit time, pharyngeal peristaltic amplitude and duration, the length of the bolus in the pharynx, and excursions of the hyoid and larynx were unaffected by body position. We conclude that intrabolus pressure is an important determinant of upper esophageal sphincter opening in the healthy oropharynx and that gravity does not influence pharyngeal bolus transport. The healthy upper esophageal sphincter has residual opening capacity that can be demonstrated by altering body posture.

Effect of gastro-oesophageal reflux on upper oesophageal sphincter motility in children

Motor events of the upper oesophageal sphincter associated with gastro-oesophageal reflux were evaluated in 53 symptomatic children (median age 13 months) who were studied recumbent and unsedated. Children were divided into four groups according to symptoms, and then into two groups according to the presence or absence of neurological deficit. No grouping had basal upper oesophageal sphincter pressure that differed significantly from any other. Oesophageal distention due to gastro-oesophageal reflux, which was recognisable as oesophageal common cavity episodes, was associated with augmentation of mean basal upper oesophageal sphincter pressure from 36.5 (SD 18) mm Hg to 48.5 (18) mm Hg (p < 0.0001), irrespective of whether gastro-oesophageal reflux caused oesophageal acidification. Abrupt relaxations of the upper oesophageal sphincter independent of swallowing and lasting up to three seconds occurred during 54% of common cavity episodes. Forty nine per cent of these relaxations occurred within four seconds after the onset of distention. The oesophageal distention caused by gastro-oesophageal reflux is a potent stimulus of transient upper oesophageal sphincter relaxations in children. These relaxations are a more likely explanation for oesophagopharyngeal reflux than defective basal upper oesophageal sphincter tone.