1,721,061 research outputs found
Evaluation of toddlers different strategies during the first 6 months of independent walking: A longitudinal study
No full textIntroduction and aim: Many studies have been observing infants at the onset of walking in order to evaluate the development of different strategies and coordination [1,2]. These studies regard most of the times small groups (20) using inertial sensors over a 6-months period after onset of independent walking. These data will allow evaluating the changes in gait temporal parameters and coordination at the beginning of independent walking. Moreover they will permit to evaluate quantitatively differences in strategies at the very beginning of walking [5] and to eventually correlate these differences with children characteristics.
Patients/materials and methods: Twenty healthy infants (77 ± 3 cm, 10 ± 2 kg, 13 ± 2 months) were included in the study. All of the infants were full-term at birth and had no known developmental delays. Tests on the infants were scheduled once a month after the onset of independent walking for 3 months and one after 6 months. When possible, a test during the very first week of independent walking was performed. Three tri-axial wireless inertial sensors (OPALS, Apdm, USA) were mounted respectively on the lower back and on the two legs. The participants were asked to freely walk in a corridor. Ten consecutive strides were analyzed. Right heel strike (HS) and toe off (TO) instants were estimated from the angular velocity of the lower limb [6]. Stride (strT), swing (swT), stance (stanceT) times, cadence (Cad) and normalized cadence (nCad) were calculated. Trunk accelerations were used to estimate step and stride regularity (stepR and strR) [7], peak to peak range and variability of trunk accelerations. Median, 25° and 75° percentiles of estimated parameters were calculated at each developmental stage.
Results: StrT decreased from month 0 to month 2 and then increased with months of experience. The opposite trend was shown by Cad and nCad. StT followed the same trend of StrT, while SwT increased constantly with months of experience. StepR and strR did not show a general trend for all the children. Medio-lateral trunk accelerations showed a constant decrease in peak to peak range and variability in all the children.
Discussion and conclusions: The trend of Cad and nCad found is in contrast to what found by Looper (2012) [2] in longitudinal study on 8 children but is in agreement with Sutherland [8] who analysed a large number of subjects of different ages (children to adults). An analysis of different children characteristics (e.g. age at the first test) could be interesting for explaining these different results. The low swT at the very beginning of walking could be an evidence of children fear of falling. StepR and strR did not show a general trend among the whole group: future works will focus on evaluating if there are two or more typical trends in the whole group or if regularity is not a significant descriptive index for toddlers. Variability and peak to peak range of trunk medio-lateral accelerations decreased with experience indicating a more and more regular and less and less oscillating gait.
Future works will evaluate the possibility of identifying the strategies descripted by McCollum [5] by sensor data and to describe quantitatively how these strategies develop towards the pendulum mechanism with experience.
Acknowledgments: This research was funded by the project “Fall risk estimation and prevention in the elderly using a quantitative multifactorial approach” (project ID number 2010R277FT) awarded by MIUR
Orbital stability of walking: in-silico assessment of a walking model
No full textNonlinear methods, like orbital stability analysis,
are gaining much interest in biomechanics due to their possible
application in locomotor stability assessment. Nevertheless, still
the use of this technique in the assessment of fall risk has been
deemed controversial; one reason could lie in the lack of a
standard implementation, particularly in terms of state space
composition and number of necessary strides. It is also yet not
clear how experimental noise can affect stability results. The
aim of this study was to explore how different analysis
implementations affect stability results of a stable walking
model, and the influence of simulated experimental noise on the
results
Motor stability evaluation in elderly subjects through instrumental stability measures and clinical rating scales
No full textMain topics: Experimental studies in human movement science; Movement deviation indexes
Introduction and aim: Falls in the elderly represent a major community and public health problem, with large clinical and economic consequences [1]. The understanding of locomotor stability is a critical issue in clinical assessment procedures. Clinicians typically use clinical rating scales of motor function tests for fall risk assessment purposes. However, this approach highly relies on the clinician's subjective judgement [2]. Variability and stability measurements of stride time and trunk accelerations during gait resulted promising in the assessment of gait stability and fall risk in healthy elderly subjects [3] and could lead to a more reliable and objective quantification of motor function, potentially representing a valid and objective complement to clinical rating scales. For an effective exploitation in clinical practice, the association between stability measures and clinical scales has to be assessed. The aim of the present study is the assessment of the relationship between instrumental variability and stability measures based on trunk accelerations during gait and some widely used clinical rating scales.
Patients/materials and methods: Seventy community dwelling old adults (35 males and 35 females, 76 ± 7 years, 76 ± 13 kg, 168 ± 9 cm) participated in the study. Barthel Index (BI), Cumulative Illness Rating Scale (CIRS) and Mini-BESTest (MBT) were administered to subjects by the same operators. Due to time/location constraints, MBT was only administered to 39 subjects (19 males and 20 females, 76 ± 6 years, 77 ± 12 kg, 168 ± 8 cm). Subjects also performed an instrumented over-ground gait task (on a 100 m long road) wearing an IMU located on the trunk, at the height of the fifth lumbar vertebra. Eleven gait variability/stability measures were calculated on stride time and trunk acceleration data during gait, namely Standard Deviation (SD), Coefficient of Variation (CV), Nonstationary Index (NI), Inconsistency of Variance (IV), Poincaré Plots (PSD1/PSD2), Maximum Floquet Multipliers (maxFM), short/long-term Lyapunov exponents (sLE/lLE), Harmonic Ratio (HR), Index of Harmonicity (IH), Multiscale Entropy (MSE) and Recurrence Quantification Analysis (RQA). Each measure was calculated for anterior–posterior (AP), medio-lateral (ML) and vertical (V) acceleration directions. In order to assess the correlation between clinical parameters and variability/stability measures, log transformed measures were used as inputs for linear regression models.
Results: SD, CV, PSD1 and PSD2 showed negative correlation with BI and MBT. The only stability measure that correlated (positively) with MBT and BI was IH in the ML direction. CIRS correlated with MSE (ML and V directions), maxFM and lLE.
Discussion and conclusions: BI and MBT negatively correlated with stride time variability measures, meaning that a relationship exists between the deterioration of the overall motor functionality and the increase in stride time variability. BI and MBT were also found to be linked to the harmonicity of acceleration signal in the ML direction, confirming the importance of ML trunk oscillations during gait for functionality assessment. CIRS correlated with stability measures, in particular with MSE in ML and V directions, suggesting a link between cumulative illness and gait stability in elderly subjects. Moreover, MSE was previously found to be linked to fall history in elderly subjects, and should hence to be taken into consideration for gait stability assessment.
In conclusion, gait variability and stability measures showed promising correlation with clinical rating scales in the elderly population, and could be considered for complementing the standard clinical scores in the assessment of fall risk. A more reliable quantification of locomotor features could be obtained from instrumental measurements, allowing to avoid inter-operator differences
Environmental performance of a metal-supported protonic ceramic cell and an electrolyte-supported solid oxide cell for steam electrolysis
Full text linkCurrently, higher shares of renewable electricity are promoted to reduce global Greenhouse Gas (GHG) emissions and decarbonize the energy sector. Electrolysis can help their integration into the grid but also for energy vector production. In this context, Protonic Ceramic Electrolysis Cells (PCEC) are considered a promising clean energy technology. The ARCADE project focused on developing a cost-effective metal supported Protonic Ceramic Cell (PCC) reactor. Its environmental performance is compared to an existing Solid Oxide Electrolysis Cell (SOEC) using Life Cycle Assessment (LCA). Results show that the faradaic efficiency heavily influences a PCC's environmental performance while manufacturing has minimal impact except for potential human health concerns from metal use. To get more detailed results, further studies on PCC performance, degradation and effect of scaling up from single cells to larger systems are needed but, already at the current state, PCCs show potential for clean energy
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Measures of gait stability: performance on adults and toddlers at the beginning of independent walking
Full text linkBackground: Quantifying gait stability is a topic of high relevance and a number of possible measures have been proposed. The problem in validating these methods is the necessity to identify a-priori unstable individuals. Since proposed methods do not make any assumption on the characteristics of the subjects, the aim of the present study was to test the performance of gait stability measures on individuals whose gait is a-priori assumed unstable: toddlers at the onset of independent walking. Methods. Ten toddlers, ten adults and ten elderly subjects were included in the study. Data from toddlers were acquired longitudinally over a 6-month period to test if the methods detected the increase in gait stability with experience, and if they could differentiate between toddlers and young adults. Data from elderly subjects were expected to indicate a stability value in between the other two groups. Accelerations and angular velocities of the trunk and of the leg were measured using two tri-axial inertial sensors. The following methods for quantifying gait stability were applied: stride time variability, Poincaré plots, harmonic ratio, short term Lyapunov exponents, maximum Floquet multipliers, recurrence quantification analysis and multiscale entropy. An unpaired t-test (level of significance of 5%) was performed on the toddlers and the young adults for each method and, for toddlers, for each evaluated stage of gait development. Results: Methods for discerning between the toddler and the adult groups were: stride time variability, Poincaré plots, harmonic ratio, short term Lyapunov exponents (state space composed by the three linear accelerations of the trunk), recurrence quantification analysis and multiscale entropy (when applied on the vertical or on the antero-posterior L5 accelerations). Conclusions: Results suggested that harmonic ratio and recurrence quantification analysis better discern gait stability in the analyzed subjects, differentiating not only between unstable toddlers and stable healthy adults, but also evidencing the expected trend of the toddlers towards a higher stability with walking experience, and indicating elderly subjects as stable as or less stable than young adults
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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