An Exploratory Approach to Manipulating Dynamic Stability: Investigating the Role of Visual Control during a Precision Foot Placement Task

ABSTRACT Background: The visual system provides the body with an accurate sensory system; designed to gather information at a distance and acts as a feedforward control mechanism during human locomotion. By doing so, visual information contributes coordination of the head-arm-trunk (HAT) segment and modulating foot placement. The purpose of this study was to examine the effects of a constrained pathway during a complex navigational stone-stepping task on HAT segment control and how the visual system guides locomotion during a complex foot placement task. Methods: Nine university-aged females (Mean age: 22.5 years old +/-1.75) participated in this study. Participants were instrumented with four rigid bodies (4x3 IRED markers) on the head, trunk and feet and two IRED markers on the wrists in order to measure kinematic data, collected by Optotrak system (NDI, Waterloo, Canada). Additionally, each participant was outfitted with an ASL H7-HS High Speed Head Mounted Optics (ASL, Bedford, USA) eye tracking unit to assess gaze behaviours. The experimental protocol required participants to perform 40 walking trials across four conditions (i.e., constrained and self-selected pathways; starting with either the left or the right foot), on a 7.2m x 1.2m raised-target platform. The platform consisted of 60 sloper-style rock climbing holds, whose location was designed to satisfy one of three criterion: 1) in line with natural footfall locations (e.g. normal step length and/or width dimensions of 60cm by 10cm); 2) greater or less than one of the dimensions of a natural step length or width; or 3) to act as a possible option/distractor on the pathway. The two constrained pathways were indicated with a high-contrasting moldable material placed inside each hold’s screw hole. Measurements were compared across conditions (i.e., constrained versus unconstrained), time points (e.g. first, middle, and last trial performed of each condition), and segment (Segment 1: first 3m of path or Segment 2: last 3m of path). The measurements included: horizontal and vertical pupil velocity RMS; average walking speed; trunk rotations about the hip (i.e., pitch and roll), and whole-body movement (i.e., ML COM variability). Results: Findings revealed that there was a significant difference between conditions such that: 1) the constrained vertical pupil RMS velocity was higher than the unconstrained (F(3,24)=4.71; p= .04; d=.46); 2) the unconstrained horizontal pupil RMS velocity was higher than the unconstrained (F(3,24)=4.40; p= .03; d=.36); 3) the constrained average walking speed was greater than the unconstrained (F(3,24)=23.27; p=0.04; d=.30); 4) the constrained trunk roll was greater than the unconstrained (F(3,21)=4.84; p=0.01; d=.45); and 5) the unconstrained dynamic stability margin minimum (DSMmin) was greater than the constrained (F(3,21)=4.89; p= .01; d=.41). Conclusions: The complex nature of the raised-target foot placement task challenged individuals from the start of each condition, forcing participants to learn how to control body movements—especially in the AP direction. During constrained condition, there was evidence to suggest that there was a greater regulation of trunk control than during unconstrained trials. This was attributed to the conditional demands of predetermined pathway to follow. However, during unconstrained trials, individuals were able to choose footholds, which were most likely based on their current state of stability. And thus, conditional demands of the pathway influenced gaze behaviours, such that during the constrained condition participants used a scanning behaviour (i.e., greater vertical pupil velocity RMS) whereas participants used more of a sampling behaviour (i.e., greater horizontal and slower vertical pupil velocities) during the free choice pathway condition. Therefore, the finding from this study suggest that gaze behaviours are influenced by stepping characteristics and these different gaze behaviours have different effects on trunk control

An Exploratory Approach to Manipulating Dynamic Stability: Investigating the Role of Visual Control during a Precision Foot Placement Task

ABSTRACT Background: The visual system provides the body with an accurate sensory system; designed to gather information at a distance and acts as a feedforward control mechanism during human locomotion. By doing so, visual information contributes coordination of the head-arm-trunk (HAT) segment and modulating foot placement. The purpose of this study was to examine the effects of a constrained pathway during a complex navigational stone-stepping task on HAT segment control and how the visual system guides locomotion during a complex foot placement task. Methods: Nine university-aged females (Mean age: 22.5 years old +/-1.75) participated in this study. Participants were instrumented with four rigid bodies (4x3 IRED markers) on the head, trunk and feet and two IRED markers on the wrists in order to measure kinematic data, collected by Optotrak system (NDI, Waterloo, Canada). Additionally, each participant was outfitted with an ASL H7-HS High Speed Head Mounted Optics (ASL, Bedford, USA) eye tracking unit to assess gaze behaviours. The experimental protocol required participants to perform 40 walking trials across four conditions (i.e., constrained and self-selected pathways; starting with either the left or the right foot), on a 7.2m x 1.2m raised-target platform. The platform consisted of 60 sloper-style rock climbing holds, whose location was designed to satisfy one of three criterion: 1) in line with natural footfall locations (e.g. normal step length and/or width dimensions of 60cm by 10cm); 2) greater or less than one of the dimensions of a natural step length or width; or 3) to act as a possible option/distractor on the pathway. The two constrained pathways were indicated with a high-contrasting moldable material placed inside each hold’s screw hole. Measurements were compared across conditions (i.e., constrained versus unconstrained), time points (e.g. first, middle, and last trial performed of each condition), and segment (Segment 1: first 3m of path or Segment 2: last 3m of path). The measurements included: horizontal and vertical pupil velocity RMS; average walking speed; trunk rotations about the hip (i.e., pitch and roll), and whole-body movement (i.e., ML COM variability). Results: Findings revealed that there was a significant difference between conditions such that: 1) the constrained vertical pupil RMS velocity was higher than the unconstrained (F(3,24)=4.71; p= .04; d=.46); 2) the unconstrained horizontal pupil RMS velocity was higher than the unconstrained (F(3,24)=4.40; p= .03; d=.36); 3) the constrained average walking speed was greater than the unconstrained (F(3,24)=23.27; p=0.04; d=.30); 4) the constrained trunk roll was greater than the unconstrained (F(3,21)=4.84; p=0.01; d=.45); and 5) the unconstrained dynamic stability margin minimum (DSMmin) was greater than the constrained (F(3,21)=4.89; p= .01; d=.41). Conclusions: The complex nature of the raised-target foot placement task challenged individuals from the start of each condition, forcing participants to learn how to control body movements—especially in the AP direction. During constrained condition, there was evidence to suggest that there was a greater regulation of trunk control than during unconstrained trials. This was attributed to the conditional demands of predetermined pathway to follow. However, during unconstrained trials, individuals were able to choose footholds, which were most likely based on their current state of stability. And thus, conditional demands of the pathway influenced gaze behaviours, such that during the constrained condition participants used a scanning behaviour (i.e., greater vertical pupil velocity RMS) whereas participants used more of a sampling behaviour (i.e., greater horizontal and slower vertical pupil velocities) during the free choice pathway condition. Therefore, the finding from this study suggest that gaze behaviours are influenced by stepping characteristics and these different gaze behaviours have different effects on trunk control

Doppler lidar observations of sensible heat flux and intercomparisons with a ground-based energy balance station and WRF model output

This is an open access article - Copyright @ 2009 E. Schweizerbart'sche VerlagsbuchhandlungDuring the Convective and Orographically induced Precipitation Study (COPS), a scanning Doppler lidar was deployed at Achern, Baden-Wüttemberg, Germany from 13th June to 16th August 2007. Vertical velocity profiles ('rays') through the boundary layer were measured every 3 seconds with vertical profiles of horizontal wind velocity being derived from performing azimuth scans every 30 minutes. During Intense Observation Periods radiosondes were launched from the site. In this paper, a case study of convective boundary layer development on 15th July 2007 is investigated. Estimates of eddy dissipation rate are made from the vertically pointing lidar data and used as one input to the velocity-temperature co-variance equation to estimate sensible heat flux. The sensible heat flux values calculated from Doppler lidar data are compared with a surface based energy balance station and output from the Weather Research and Forecasting (WRF) model.Funding is obtained from NER

Numerical study of guided modes in arrays of metallic nanowires

We numerically investigate the band structure and guided modes within arrays of metallic nanowires. We show that bandgaps appear for a range of array geometries and that these can be used to guide light in these structures. Values of attenuation as low as 1.7 dB/cm are predicted for arrays of silver wires at communications wavelengths. This is more than 100 times smaller than the attenuation of the surface plasmon polariton modes on a single silver nanowire. © 2007 Optical Society of America

Models for guidance in kagome-structured hollow-core photonic crystal fibres

We demonstrate by numerical simulation that the general features of the loss spectrum of photonic crystal fibres (PCF) with a kagome structure can be explained by simple models consisting of thin concentric hexagons or rings of glass in air. These easily analysed models provide increased understanding of the mechanism of guidance in kagome PCF, and suggest ways in which the high-loss resonances in the loss spectrum may be shifted. © 2007 Optical Society of America

Conservative management of grade 1V renal injury with complete transection: a case report

The expectant management of high grade renal injuries in hemodynamically stable children has gained increasing acceptance amongst paediatric surgeons. However, patients with grade 1V injury with complete renal transection have been identified as a subgroup with a poor outcome that may benefit from early operative intervention

Do children\u27s food preferences align with dietary recommendations?

Objectives: To examine how Australian children\u27s reported everyday food preferences reflect dietary recommendations, and the impact of sociodemographic factors on these associations.Design:&nbsp; Cross-sectional survey.Setting/subjects: Three hundred and seventy-one parents of children aged 2&ndash;5 years, recruited from three socio-economic groups in two Australian cities, completed a survey on their child\u27s liking for 176 foods and drinks on a 5-point Likert scale in addition to demographic descriptors. Preferences were compared with the recommendations of the Dietary Guidelines for Children and Adolescents in Australia and the Australian Guide to Healthy Eating.Results:&nbsp; Foods in the Extra Foods (non-nutritious foods) and Cereals groups of the Australian Guide to Healthy Eating were highly liked (mean: 4.02 and 4.01, respectively), whilst foods in the Vegetables group were liked least (mean: 3.01). A large percentage of foods in the Cereals and Extra Foods groups were liked (64% and 56%, respectively) in contrast to the other food groups, especially Vegetables (7%). Children liked foods that were higher in sugar (r = 0.29, P &lt; 0.0001) and more energy-dense (r = 0.34, P &lt; 0.0001) but not those higher in saturated fat (r = 0.16, P = 0.03), total fat (r = 0.12, P = 0.12) or sodium (r = 0.10, P = 0.18). Sociodemographic variables (e.g. socio-economic status, parental education, children\u27s age and sex) explained little of the variation in children\u27s food preferences.Conclusions:&nbsp; Australian pre-school children\u27s food preferences align with dietary guidelines in some respects, but not others. Interventions are needed to shift children\u27s preferences away from non-nutritious foods that are high in energy density and sugar, and towards vegetables and fruits.<br /

Infant Feeding Websites and Apps: A Systematic Assessment of Quality and Content

Background: Internet websites and smartphone apps have become a popular resource to guide parents in their children&rsquo;s feeding and nutrition. Given the diverse range of websites and apps on infant feeding, the quality of information in these resources should be assessed to identify whether consumers have access to credible and reliable information.Objective: This systematic analysis provides perspectives on the information available about infant feeding on websites and smartphone apps.Methods: A systematic analysis was conducted to assess the quality, comprehensibility, suitability, and readability of websites and apps on infant feeding using a developed tool. Google and Bing were used to search for websites from Australia, while the App Store for iOS and Google Play for Android were used to search for apps. Specified key words including baby feeding, breast feeding, formula feeding and introducing solids were used to assess websites and apps addressing feeding advice. Criteria for assessing the accuracy of the content were developed using the Australian Infant Feeding Guidelines.Results: A total of 600 websites and 2884 apps were screened, and 44 websites and 46 apps met the selection criteria and were analyzed. Most of the websites (26/44) and apps (43/46) were noncommercial, some websites (10/44) and 1 app were commercial and there were 8 government websites; 2 apps had university endorsement. The majority of the websites and apps were rated poor quality. There were two websites that had 100% coverage of information compared to those rated as fair or poor that had low coverage. Two-thirds of the websites (65%) and almost half of the apps (47%) had a readability level above the 8th grade level.Conclusions: The findings of this unique analysis highlight the potential for website and app developers to merge user requirements with evidence-based content to ensure that information on infant feeding is of high quality. There are currently no apps available to consumers that address a variety of infant feeding topics. To keep up with the rapid turnover of the evolving technology, health professionals need to consider developing an app that will provide consumers with a credible and reliable source of information about infant feeding, using quality assessment tools and evidence-based content

Caudate lobe resections: a single-center experience and evaluation of factors predictive of outcomes

BACKGROUND: Despite the increasing frequency of liver resection for multiple types of disease, caudate lobe resection remains a rare surgical event. The goal of this study is to review our experience and evaluate possible predictors of adverse outcomes in patients undergoing caudate lobectomy. METHODS: We reviewed a 1,900-patient prospective hepato-pancreatico-biliary database from January 2000 to December 2011, identifying 36 hepatectomy patients undergoing caudate lobe resection. Clinicopathologic characteristic and outcome data were compared using chi-square, T-test, ANOVA, Kaplan-Meier, and Cox regression analysis. Primary endpoints were the incidence and severity of complications, and secondary endpoints were blood loss, hospital stay, and transfusion requirements. Patients were also divided in two groups with group A being patients operated on before December 2007 and group B after 2007. We compared the demographics, risk factors, complication rates, and operative details between the two groups. RESULTS: Thirty-six patients underwent caudate lobe resection for cholangiocarcinoma (47.2%), metastatic colorectal cancer (36.1%), hepatocellular carcinoma (8.3%), or benign disease (8.3%). Nine patients (29%) had additional liver resection. Median overall survival (OS) was 21 months. Complications occurred in 52.7% (19/36) of patients with a median grade of 2. Tobacco abuse was associated with an increased risk of operative complications (73.3% vs. 38.9%, p = 0.03). Prior history of cardiac disease was associated with a higher complication rate (87% vs. 42%, p = 0.03). Neoadjuvant chemotherapy, biliary procedures, hepatitis, and prior major abdominal surgery were not predictive of complications. Major complication was also predicted by the volume of RBC transfusion (2.7 vs. 4.1 units, p = 0.003). In our subgroup analysis of the patients undergoing surgery before and after 2007, the two groups were well matched based on age, comorbidities, and risk factors. The complication rates and rates of high-grade complications were similar, but blood loss (600 ml vs. 400 ml, p = 0.03), inflow occlusion time (Pringle time 12.6 vs. 6, p = 0.00), and hospital stay (9.5 vs. 7 days, p = 0.01) were significantly lower in group B. CONCLUSIONS: With appropriate patient selection, caudate lobe resection is an effective component of surgery for hepatic disease. Tobacco use and prior cardiac history increase the risk of complications

A qualitative study of the infant feeding beliefs and behaviours of mothers with low educational attainment

© 2016 Russell et al. Background: Infancy is an important period for the promotion of healthy eating, diet and weight. However little is known about how best to engage caregivers of infants in healthy eating programs. This is particularly true for caregivers, infants and children from socioeconomically disadvantaged backgrounds who experience greater rates of overweight and obesity yet are more challenging to reach in health programs. Behaviour change interventions targeting parent-infant feeding interactions are more likely to be effective if assumptions about what needs to change for the target behaviours to occur are identified. As such we explored the precursors of key obesity promoting infant feeding practices in mothers with low educational attainment. Methods: One-on-one semi-structured telephone interviews were developed around the Capability Opportunity Motivation Behaviour (COM-B) framework and applied to parental feeding practices associated with infant excess or healthy weight gain. The target behaviours and their competing alternatives were (a) initiating breastfeeding/formula feeding, (b) prolonging breastfeeding/replacing breast milk with formula, (c) best practice formula preparation/sub-optimal formula preparation, (d) delaying the introduction of solid foods until around six months of age/introducing solids earlier than four months of age, and (e) introducing healthy first foods/introducing unhealthy first foods, and (f) feeding to appetite/use of non-nutritive (i.e., feeding for reasons other than hunger) feeding. The participants' education level was used as the indicator of socioeconomic disadvantage. Two researchers independently undertook thematic analysis. Results: Participants were 29 mothers of infants aged 2-11 months. The COM-B elements of Social and Environmental Opportunity, Psychological Capability, and Reflective Motivation were the key elements identified as determinants of a mother's likelihood to adopt the healthy target behaviours although the relative importance of each of the COM-B factors varied with each of the target feeding behaviours. Conclusions: Interventions targeting healthy infant feeding practices should be tailored to the unique factors that may influence mothers' various feeding practices, taking into account motivational and social influences