Current Issue : April - June Volume : 2014 Issue Number : 2 Articles : 4 Articles
Background: The information of electromyographic signals can be used by\r\nMyoelectric Control Systems (MCSs) to actuate prostheses. These devices allow the\r\nperforming of movements that cannot be carried out by persons with amputated\r\nlimbs. The state of the art in the development of MCSs is based on the use of individual\r\nprincipal component analysis (iPCA) as a stage of pre-processing of the classifiers. The\r\niPCA pre-processing implies an optimization stage which has not yet been deeply\r\nexplored.\r\nMethods: The present study considers two factors in the iPCA stage: namely A (the\r\nfitness function), and B (the search algorithm). The A factor comprises two levels,\r\nnamely A1 (the classification error) and A2 (the correlation factor). Otherwise, the B factor\r\nhas four levels, specifically B1 (the Sequential Forward Selection, SFS), B2 (the Sequential\r\nFloating Forward Selection, SFFS), B3 (Artificial Bee Colony , ABC), and B4 (Particle\r\nSwarm Optimization, PSO). This work evaluates the incidence of each one of the eight\r\npossible combinations between A and B factors over the classification error of the MCS.\r\nResults: A two factor ANOVA was performed on the computed classification errors\r\nand determined that: (1) the interactive effects over the classification error are not\r\nsignificative (F0.01,3,72 = 4.0659 > fAB = 0.09), (2) the levels of factor A have significative\r\neffects on the classification error (F0.02,1,72 = 5.0162 < fA = 6.56), and (3) the levels of\r\nfactor B over the classification error are not significative (F0.01,3,72 = 4.0659 > fB = 0.08).\r\nConclusions: Considering the classification performance we found a superiority of\r\nusing the factor A2 in combination with any of the levels of factor B. With respect to the\r\ntime performance the analysis suggests that the PSO algorithm is at least 14 percent\r\nbetter than its best competitor. The latter behavior has been observed for a particular\r\nconfiguration set of parameters in the search algorithms. Future works will investigate\r\nthe effect of these parameters in the classification performance, such as length of the\r\nreduced size vector, number of particles and bees used during optimal search, the\r\ncognitive parameters in the PSO algorithm as well as the limit of cycles to improve a\r\nsolution in the ABC algorithm....
Background: Measurements of the morphology of the ankle joint, performed mostly\r\nfor surgical planning of total ankle arthroplasty and for collecting data for total ankle\r\nprosthesis design, are often made on planar radiographs, and therefore can be very\r\nsensitive to the positioning of the joint during imaging. The current study aimed to\r\ncompare ankle morphological measurements using CT-generated 2D images with\r\ngold standard values obtained from 3D CT data; to determine the sensitivity of the\r\n2D measurements to mal-positioning of the ankle during imaging; and to quantify\r\nthe repeatability of the 2D measurements under simulated positioning conditions\r\ninvolving random errors.\r\nMethod: Fifty-eight cadaveric ankles fixed in the neutral joint position (standard\r\npose) were CT scanned, and the data were used to simulate lateral and frontal\r\nradiographs under various positioning conditions using digitally reconstructed\r\nradiographs (DRR).\r\nResults and discussion: In the standard pose for imaging, most ankle morphometric\r\nparameters measured using 2D images were highly correlated (R > 0.8) to the gold\r\nstandard values defined by the 3D CT data. For measurements made on the lateral\r\nviews, the only parameters sensitive to rotational pose errors were longitudinal\r\ndistances between the most anterior and the most posterior points of the tibial mortise\r\nand the tibial profile, which have important implications for determining the optimal\r\ncutting level of the bone during arthroplasty. Measurements of the trochlea tali width\r\non the frontal views underestimated the standard values by up to 31.2%, with only a\r\nmoderate reliability, suggesting that pre-surgical evaluations based on the trochlea tali\r\nwidth should be made with caution in order to avoid inappropriate selection of\r\nprosthesis sizes.\r\nConclusions: While highly correlated with 3D morphological measurements, some 2D\r\nmeasurements were affected by the bone poses in space during imaging, which may\r\naffect surgical decision-making in total ankle arthroplasty, including the amount of bone\r\nresection and the selection of the implant sizes. The linear regression equations for the\r\nrelationship between 2D and 3D measurements will be helpful for correcting the errors\r\nin 2D morphometric measurements for clinical applications....
Background: The aim of this in vitro study was the evaluation of the mechanical\r\nproperties the screws for rapid maxillary expansion (RME).\r\nMethods: Three commercially available screws for RME were tested: Leone A2620;\r\nDentaurum Hyrax; Forestadent Palatal Split Screw. All expansion screws were 10 mm\r\nin size. For the evaluation of mechanical properties, the screws for RME were\r\nadjusted using the same maxillary dental model. An Instron 3365 testing machine\r\nwith a load cell of 5 kN recorded the forces released by the screws at different\r\namounts of activation (1, 5, 10, 15 and 20 quarters of a turn). Each type of screw was\r\ntested 10 times. Comparisons between the forces released by the different types of\r\nscrews at different amounts of activation were carried out by means of analysis of\r\nKruskal-Wallis test with post-hoc test di Tukey (P < 0.05).\r\nResults: The results of this study showed that all 3 expansion devices were able to\r\ndevelop forces that could produce a separation of the palatine processes. The Hyrax\r\nand A2620 expanders developed force values over 20 kg and the Palatal Split screws\r\nabout 16 kg. Both the A2620 and Hyrax expanders showed significantly greater\r\namounts of forces at all the different amounts of activations with respect to the\r\nPalatal Split screw.\r\nConclusions: All tested devices showed the capability of developing expansion\r\nforces (16-20 kg) adequate for RME. The A2620 and Hyrax expanders showed a\r\ngreater level of rigidity than the Palatal Split screw....
Background: Continuous and discrete wavelet transforms have been established as\r\nvalid tools to analyze non-stationary and transient signals over Fourier domain methods.\r\nAdditionally, Fourier transform based coherence methods provide aggregate results but\r\ndo not provide insights into the changes in coherent behavior over time, hence limiting\r\ntheir utility.\r\nMethods: Statistical validation of the wavelet transform coherence (WTC) was\r\nconducted with simulated data sets. Time frequency maps of signal coherence between\r\ncalf muscle electromyography (EMG) and blood pressure (BP) were obtained by WTC to\r\nprovide further insight into their interdependent time-varying behavior via the skeletal\r\nmuscle pump during quiet stance. Data were collected from healthy young males (n = 5,\r\n19ââ?¬â??28 years) during a quiet stance on a balance platform. Waveforms for EMG and BP\r\nwere acquired and processed for further analysis.\r\nResults: Low values of bias and standard deviation (< 0.1) were observed and the use of\r\nboth simulated and real data demonstrated that the WTC method was able to identify\r\ntime points of significant coherence (> Threshold) and objectively detect existence of\r\ninterdependent activity between the calf muscle EMG and blood pressure.\r\nConclusions: The WTC method effectively identified the presence of linear coupling\r\nbetween the EMG and BP signals during quiet standing. Future studies with more\r\nhuman data are needed to establish the exact characteristics of the identified\r\nrelationship....
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