Fractal analysis features for weak and single-channel upper-limb EMG signals

Electromyography (EMG) signals are the electrical manifestations of muscle contractions. EMG signals may be weak or at a low level when there is only a small movement in the major corresponding muscle group or when there is a strong movement in the minor corresponding muscle group. Moreover, in a single-channel EMG classification identifying the signals may be difficult. However, weak and single-channel EMG control systems offer a very convenient way of controlling human–computer interfaces (HCIs). Identifying upper-limb movements using a single-channel surface EMG also has a number of rehabilitation and HCI applications. The fractal analysis method, known as detrended fluctuation analysis (DFA), has been suggested for the identification of low-level muscle activations. This study found that DFA performs better in the classification of EMG signals from bifunctional movements of low-level and equal power as compared to other successful and commonly used features based on magnitude and other fractal techniques.     

Infection risk in patients with rheumatoid arthritis treated with etanercept or adalimumab

Objectives

To compare the risk of infection for rheumatoid arthritis (RA) patients who took etanercept or adalimumab medication in a nationwide population.

Methods

RA patients who took etanercept or adalimumab were identified in the Taiwan's National Health Insurance Research Database. The composite outcome of serious infections, including hospitalization for infection, reception of an antimicrobial injection, and tuberculosis were followed for 365 days. A Kaplan–Meier survival curve with a log-rank test and Cox proportional hazards regression were used to compare risks of infection between the two cohorts of tumor necrosis factor (TNF)-α antagonists users. Hazard ratios (HRs) were obtained and adjusted with propensity scores and clinical factors. Sensitivity analyses and subgroup analyses were also performed.

Results

In total, 1660 incident etanercept users and 484 incident adalimumab users were eligible for the analysis. The unadjusted HR for infection of the etanercept users was significantly higher than that of the adalimumab users (HR: 1.93; 95% confidence interval (CI): 1.09–3.42; p = 0.024). The HRs were 2.04 (95% CI: 1.14–3.65; p = 0.016) and 2.02 (95% CI: 1.13–3.61; p = 0.018) after adjusting for propensity scores and for propensity scores in addition to clinical factors, respectively. The subgroup analyses revealed that HRs for composite infection was significantly higher in patient subgroups of older age, female, as well as patients who did not have DM, COPD, and hospitalization history at the baseline.

Conclusion

In this head-to-head cohort study involving a nationwide population of patients with RA, etanercept users demonstrated a higher risk of infection than adalimumab users. Results of this study suggest the possible existence of an intra-class difference in infection risk among TNF-α antagonists.     

Prediction of dose escalation for rheumatoid arthritis patients under infliximab treatment

Rheumatoid arthritis (RA) is a chronic inflammatory joint disease that leads to irreversible joint destruction. To prevent this, new biological therapies, such as infliximab, have been successfully developed. The present analysis is based on an expanded access program in which 511 RA patients with chronic refractory disease were treated with infliximab. They received a standard dose of 3 mg/kg on weeks 0, 2, 6, 14 and every 8 weeks thereafter. On week 22, the treating rheumatologist evaluated the situation of every patient and decided whether the current dose should be increased or not. This decision can be considered as a measure of insufficient response. In the present analysis, 3 machine-learning classification techniques—the self-organizing map (SOM), multilayered perceptron (MLP) and support vector machine (SVM)—are implemented to model the decision to give a dose increase. Their performance on increasingly multivariate real-life data will be studied and compared to classical statistics—linear discriminant analysis (LDA) and logistic regression (LR). Results show that the SOM is an excellent tool for data visualization but not for classification. All the remaining methods show good classification performance, if configured well. However, as the number of features increases, the performance decreases. The SVM suffers to a lesser degree from this curse of dimensionality. Expectation maximization (EM) comes out as a good method to cope with missing values in such real-life data.     

Fractal indexing with the joint statistical properties and its application in texture image retrieval

Fractal image coding is a block-based scheme that exploits the self-similarity hiding within an image. Fractal parameters generated by the block-based scheme are quantitative measurements of self-similarity, and therefore they can be used to construct image signatures. By combining fractal parameters and collage error, a set of new statistical fractal signatures, such as histogram of collage error (HE), joint histogram of contrast scaling and collage error (JHSE), and joint histogram of range block mean and contrast scaling and collage error (JHMSE) is proposed. These fractal signatures effectively extract and reflect the statistical properties intrinsic in texture images. Hence, they provide new statistical features for use in texture image retrieval and identification. Furthermore, in order to reduce computational complexity of the JHMSE signature, the JHMSE signature is simplified to HM (histogram of range block mean) tJHSE and HM t HS (histogram of contrast scaling) tHE, based on the independence and distance equivalence. Mathematical analysis of the simplification scheme is also carried out. The proposed fractal signatures are compared with the existing fractal signatures. Experimental results show that the proposed signatures, HM t JHSE and HM t HS t HE, achieve a higher retrieval rate with a lower computational complexity.     

MS characterization of apheresis samples from rheumatoid arthritis patients for the improvement of immunoadsorption therapy - a pilot study

Identification of proteins from apheresis samples was performed by both SDS-PAGE and 2-D gel separation of eluted proteins from staphylococcal protein A-based immunoadsorption columns (Prosorba^®) followed by MS peptide mass fingerprinting and MS/MS peptide sequencing on a MALDI QIT TOF mass spectrometer. MS/MS peptide sequencing was performed in conjunction with a micro reversed phase HPLC configured with an online MALDI plate-spotting device. Apheresis treatment had been performed in three patients with longstanding therapy refractory rheumatoid arthritis. 2-D gels displayed ca. 500 spots representing proteins that were eluted from the Prosorba^® columns. From 54 gels, a total of 1256 protein spots had been picked and yielded in the identification of 56 non-redundant proteins without counting isoforms. Proteins from the eluates belong to five major groups comprising (i) immunoglobulins (IgG, IgA, IgM heavy and light chains; about 40% of the spots), (ii) proteins involved in coagulation, (iii) HDL/LDL-associated proteins, (iv) proteins from the complement system, and (v) acute phase proteins. MS analysis showed that the full-length C3 complement protein had been cleaved upon complement activation, presumably on the column, such that the anaphylatoxin C3a was produced and released during therapy. Our results are consistent with clinical observations on both patient responses to therapy and reported adverse events. For the first time, direct molecular information has become available to support mechanistic reasoning for the principle of function of staphylococcal protein A-based immunoadsorption therapy and for the explanation of adverse events. According to our results, removal and/or modulation of immune complexes together with complement activation can be regarded as the major events that are taking place during Prosorba^® therapy. In order to avoid complement activation and induction of an inflammatory cascade, we suggest the prevention of C3a anaphylatoxin-related reactions during immunoadsorption therapy.     

Medical diagnosis of rheumatoid arthritis disease from right and left hand Ulnar artery Doppler signals using adaptive network based fuzzy inference system (ANFIS) and MUSIC method

Rheumatoid arthritis (RA) is a multi-systemic autoimmune disease that leads to substantial morbidity and mortality. In this paper, as spectral analysis methods of Multiple Signal Classification (MUSIC) method is used in order to extract the significant features from the right and left hand Ulnar artery Doppler signals for the diagnosis of RA disease. The MUSIC method has been used as subspace method. To extract features from Doppler signals obtained from the right and left hand Ulnar arterial the MUSIC method model degrees of 5, 10, 15, 20, and 25 were used. Then, an adaptive network based fuzzy inference system (ANFIS) was applied to features extracted from the right and left hand Ulnar artery Doppler signals for classifying RA disease. The methods are not new, but the study has a novelty in that the application area of these methods is new. In the hybrid model, the combination of MUSIC and ANFIS yielded classification accuracies of 95% (for a model degree of 20) using the right hand Ulnar artery and classification accuracies of 91.25% (for a model degree of 10) using left hand Ulnar artery Doppler signals in the diagnosis of RA disease. The proposed approach has potential to help with the early diagnosis of RA disease for the specialists who study this subject.     

Hand radiographs preprocessing, image representation in the finger regions and joint space width measurements for image interpretation

In this paper, the first stage of studies concerning the computer analysis of hand X-ray digital images is described. The images are preprocessed and then skeletization of the fingers is carried out. Then, the interphapangeal and metacarpophalangeal joints are detected and contoured. Joint widths are also measured. The obtained results largely concur with those obtained by other authors—see Beier et al. [Segmentation of medical images combining local, regional, global, and hierarchical distances into a bottom-up region merging scheme, Proc. SPIE 5747 (2005) 546-555], Klooster et al. [Automatic quantification of osteoarthritis in hand radiographs: validation of a new method to measure joint space width, Osteoarthritis and Cartilage 16 (1) (2008) 18-25], Ogiela et al. [Image languages in intelligent radiological palm diagnostics, Pattern Recognition 39 (2006) 2157-2165] and Ogiela and Tadeusiewicz [Picture languages in automatic radiological palm interpretation, Int. J. Appl. Math. Comput. Sci. 15 (2) (2005) 305-312].     

Impact of joint torques on heel acceleration at heel contact, a contributor to slips and falls

Slips/falls are a health burden in the workplace. Previous research has implied a relationship between foot dynamics at heel contact and slips/falls; however, heel acceleration has received little attention. Heel acceleration as the heel contacts the ground is the result of the combined effort of the leg joint torques to control motion of the foot. This study aims to examine the association of heel acceleration with fall risk, and explore the main joint torque determinant of heel acceleration at contact. Sixteen young and eleven older adults walked on known dry floors and in slippery environments expected to be dry. Heel acceleration at heel contact in the direction of motion, i.e. anterior/posterior, was compared between slip-recovery and slip-fall outcomes. Results showed that subjects that recovered contacted the floor with a greater heel deceleration (p < 0.05) than fall subjects. Knee torque alone explained 76% of the heel acceleration variability (p < 0.01). These data suggest that walking with reduced knee flexion torque at heel contact results in a reduced heel deceleration, a potential risk factor for slip-initiated falls.     

Preliminary comparison of respiratory signals using acceleration on neck and humidity in exhaled air

Microsystem Technologies - A microelectromechanical system is recently used for measurements of vital signs. Although the neck is regarded as an alternate observatory location of heartbeats, there...     

Bayesian analysis of Lidar signals with multiple returns

Time-Correlated Single Photon Counting and Burst Illumination Laser data can be used for range profiling and target classification. In general, the problem is to analyse the response from a histogram of either photon counts or integrated intensities to assess the number, positions and amplitudes of the reflected returns from object surfaces. The goal of our work is a complete characterisation of the 3D surfaces viewed by the laser imaging system. The authors present a unified theory of pixel processing that is applicable to both approaches based on a Bayesian framework which allows for careful and thorough treatment of all types of uncertainties associated with the data. We use reversible jump Markov chain Monte Carlo (RJMCMC) techniques to evaluate the posterior distribution of the parameters and to explore spaces with different dimensionality. Further, we use a delayed rejection step to allow the generated Markov chain to mix better through the use of different proposal distributions. The approach is demonstrated on simulated and real data, showing that the return parameters can be estimated to a high degree of accuracy. We also show some practical examples from both near and far range depth imaging.     

Compensation of velocity and/or acceleration joint saturation applied to redundant manipulator

The article describes a new method for velocity/acceleration redistribution in order to compensate joint velocity and/or acceleration saturation. The method is designed for redundant manipulators. When some of the joint velocities/accelerations are in saturation other joints compensate for the lack of the velocity and the velocity in the task space remains unchanged. Without the compensation the task space error would appear. Using the compensation method we can achieve maximal velocity/acceleration in the task space while preserving joint velocity/acceleration within limits. The method is also appropriate to compensate a torque saturation. Additionally, we have introduced a condition that shows if the compensation is kinematically and mathematically possible or not.     

Comparison of joint angle,velocity and acceleration estimators for hydraulically actuated manipulators to a novel dynamical approach

Excavators are used for a wide range of applications like earthworks and material handling. Assistance systems are becoming more common to support the operator. For monitoring and control based assistance functions the angular position, velocity and acceleration of the joints from the working implement are required. Commercial systems often use inertial measurement units, consisting of triaxial accelerometers and gyroscopes, to accomplish an estimation of those states. A novel joint angle, velocity and acceleration estimation for hydraulic manipulators is proposed and compared to state of the art methods. A decentralized kinematic filter using no information about the underlying system and a centralized kinematic filter taking the system kinematics into account are implemented as state of the art approaches. Both filters only use inertial measurement units to obtain information about the current state of the system. The novel centralized dynamic filter uses the same information as the centralized kinematic filter and extends it by a dynamic model containing additional information about the angular acceleration due to pressure readings of the hydraulic cylinders. Kalman filtering is used to combine the derived system and measurement models with the sensor information. The methods are evaluated on a material handling excavator for single and coupled movements of the working implement. The novel centralized dynamic filter enables improvements for the angular acceleration estimation compared to the decentralized and centralized kinematic filter. Less noise of the acceleration estimation and a better tracking of the actual acceleration are shown.     

Joint acceleration feedback control for robots: analysis, sensing and experiments

Independent joint control for robots is enhanced to suppress the dynamic couplings by incorporating an acceleration feedback loop that is designed in terms of its stability and ability in resisting the dynamic coupling disturbances. The sensing and modeling of joint acceleration via linear accelerometers is dealt from the viewpoint of practical implementation. Extensive experiments are conducted on a three-link direct drive robot, to mainly investigate the ability of the independent joint controller with the acceleration loop in resisting the coupling torque, and demonstrating the enhanced trajectory tracking performance. Results are given against the ones obtained by conventional independent joint control without the acceleration feedback control.     

Time-optimal parabolic interpolation with velocity,acceleration, and minimum-switch-time constraints

Time-optimal trajectories with bounded velocities and accelerations are known to be parabolic, i.e. piecewise constant in acceleration. An important characteristic of this class of trajectories is the distribution of the switch points – the time instants when the acceleration of any robot joint changes. When integrating parabolic trajectory generation into a motion planning pipeline, especially one that involves a shortcutting procedure, resulting trajectories usually contain a large number of switch points with a dense distribution. This high frequency acceleration switching intensifies joint motor wear as well as hampers the robot performance. In this paper, we propose an algorithm for planning parabolic trajectories subject to both physical bounds, i.e. joint velocity and acceleration limits, and the minimum-switch-time constraint. The latter constraint ensures that the time duration between any two consecutive switch points is always greater than a given minimum value. Analytic derivations are given, as well as comparisons with other methods to demonstrate the efficiency of our approach.     

利用肌电信号求解关节力矩的研究及应用综述

表面肌电信号(surface electromyography, sEMG)是人体的易于检测的神经信号,其富含大量人体运动信息。利用肌电信号作为输入信号,结合相关生物学模型分析肌电信号同肌肉力和对应关节力矩之间的关系,对于深入理解分析人体动力学具有重要意义。本文详细归纳总结了利用肌电信号求解人体关节力矩方法的研究成果,同时介绍神经肌肉骨骼模型的计算及优化过程,给出部分模型生理参数为之后的研究提供参照,并给出现阶段该方法在人体关节力矩求解中的应用。通过分析该求解过程中所面临的一些问题,总结出该方法的发展展望,为之后的研究提供参考。     

The effect of a new syringe design on the ability of rheumatoid arthritis patients to inject a biological medication

Self-administration of new biological medications can be difficult for Rheumatoid Arthritis patients with functional impairment and hand and dexterity limitation. Twenty-three Rheumatoid Arthritis (RA) patients participated in this study to compare preferences and injection forces using a conventional syringe and a new ergonomically designed syringe. Injection force measurements were collected in two ways: a) isometric forces, with the syringes' plungers in fixed positions (depressed halfway and fully depressed), and b) forces exerted during injection of the medication. Subjects' grip and pinch strengths were measured. A perception questionnaire gauged subjects' impressions and preferences. Subjects were capable of exerting significantly higher isometric forces using the new syringe with the plunger fixed both halfway and fully depressed. During injection of the medication, peak and mean injection forces were significantly higher, and duration was shorter, when using the new syringe. Subjects rated the new syringe higher on all twenty attributes on preference and performance. Therefore, it is expected that the new syringe will benefit self-administration of medication injection for RA patients.     

车辆称重系统中加速度的测量与分析

针对公路运输车辆载荷质量的检测采用的计量器具体积大、工作位置固定、不能做到随时随地检测载荷质量的问题,提出一种采用变极距电容传感器的车载式载荷检测装置,该装置中的加速度传感器用于测量前进方向的加速度和竖直方向的加速度.通过实验测试及分析表明,加速度在车辆称重测量中的影响比较大,因此在装置的软件部分必须予以补偿.     

高量程加速度传感器的结构优化与仿真分析

在传统双边四梁结构的基础上,优化设计了一种高量程加速度传感器结构,量程为10 000 gn。理论上对其进行了应力分析,验证了结构的合理性,并通过有限元建模对传感器进行了静态结构分析,模态分析和抗过载能力分析。在恒压源供电条件下,传感器的固有频率大于50 kHz,灵敏度理论值为18.88μV/gn,抗过载能力为20000 gn。与传统结构相比,极大地提高了高量程加速度传感器的性能。     

Adaptive multiuser receiver with joint channel and time delay estimation of CDMA signals based on the square-root unscented filter

The paper discusses an adaptive multiuser receiver for CDMA systems in which the scaled unscented filter (SUF) and the square root unscented filter (SURF) are used for joint estimation and tracking of the code delays and multipath coefficients of the received CDMA signals. The proposed channel estimators are more near-far resistant than the conventional extended Kalman filter (EKF) and present lower complexity than the conventional particle filter (PF) based methods. To present meaningful performance measures, the modified Cramer–Rao lower bound (CRLB) and computational complexity metrics are derived for the proposed and existing channel estimators. Computer simulation results demonstrate the superior performance of the proposed channel estimators. The proposed estimators are also shown to exhibit lower complexity relative to the PF.     

Stability and robustness analysis for human pointing motions with acceleration under feedback delays

Pointer acceleration is often used in computer mice and other interfaces to increase the range and speed of pointing motions without sacrificing precision during slow movements. However, the effects of pointer acceleration are not yet well understood. We use a system perspective and feedback control to analyze the effects of pointer acceleration. We use a new pointer acceleration model connected in feedback with the vector integration to endpoint model for pointing motions. When there are no feedback delays, we prove global asymptotic stability of the closed loop system for a general class of acceleration profiles. We also prove robustness under delays and perturbations by building Lyapunov–Krasovskii functionals for delay systems, and we find state performance bounds using robust forward invariance with maximal perturbation sets. The results are relevant to designing pointing interfaces, and our simulations illustrate the good performance of our control under realistic operating conditions. Copyright © 2016 John Wiley & Sons, Ltd.