A new postural stability-indicator to predict the level of fear of falling in Parkinson's disease patients

Background: Fear of falling (FoF) is defined as a lasting concern about falling that causes a person to limit or even stop the daily activities that he/she is capable of. Seventy percent of Parkinson's disease (PD) patients report activity limitations due to FoF. Timely identification of FoF is critical to prevent its additional adverse effects on the quality of life. Self-report questionnaires are commonly used to evaluate the FoF, which may be prone to human error. Objectives: In this study, we attempted to identify a new postural stability-indicator to objectively predict the intensity of FoF and its related behavior(s) in PD patients. Methods: Thirty-eight PD patients participated in the study (mean age, 61.2 years), among whom 10 (26.32) were identified with low FoF and the rest (73.68) with high FoF, based on Falls Efficacy Scale-International (FES-I). We used a limit of stability task calibrated to each individual and investigated the postural strategies to predict the intensity of FoF. New parameters (FTR i s; functional time ratio) were extracted based on the center of pressure presence pattern in different rectangular areas (i = 1, 2, and 3). The task was performed on two heights to investigate FoF-related behavior(s). Results: FTR 1/2 (the ratio between FTR 1 and FTR 2) was strongly correlated with the FES-I (r =-0.63, p < 0.001), Pull test (r =-0.65, p < 0.001), Timed Up and Go test (r =-0.57, p < 0.001), and Berg Balance Scale (r = 0.62, p < 0.001). The model of FTR 1/2 was identified as a best-fitting model to predicting the intensity of FoF in PD participants (sensitivity = 96.43, specificity = 80), using a threshold level of � 2.83. Conclusions: Using the proposed assessment technique, we can accurately predict the intensity of FoF in PD patients. Also, the FTR 1/2 index can be potentially considered as a mechanical biomarker to sense the FoF-related postural instability in PD patients. © 2020 The Author(s)

Postural control learning dynamics in Parkinson's disease: Early improvement with plateau in stability, and continuous progression in flexibility and mobility

Background: Balance training improves postural control in Parkinson's disease (PD). However, a systematic approach for the development of individualized, optimal training programs is still lacking, as the learning dynamics of the postural control in PD, over a training program, are poorly understood. Objectives: We investigated the learning dynamics of the postural control in PD, during a balance-training program, in terms of the clinical, posturographic, and novel model-based measures. Methods: Twenty patients with PD participated in a balance-training program, 3 days a week, for 6 weeks. Clinical tests assessed functional balance and mobility pre-training, mid-training, and post-training. Center-of-pressure (COP) was recorded at four time-points during the training (pre-, week 2, week 4, and post-training). COP was used to calculate the sway measures and to identify the parameters of a patient-specific postural control model, at each time-point. The posturographic and model-based measures constituted the two sets of stability- A nd flexibility-related measures. Results: Mobility- A nd flexibility-related measures showed a continuous improvement during the balance-training program. In particular, mobility improved at mid-training and continued to improve to the end of the training, whereas flexibility-related measures reached significance only at the end. The progression in the balance- A nd stability-related measures was characterized by early improvements over the first 3 to 4 weeks of training, and reached a plateau for the rest of the training. Conclusions: The progression in balance and postural stability is achieved earlier and susceptible to plateau out, while mobility and flexibility continue to improve during the balance training. © 2020 The Author(s)

A New Cryogenic Apparatus to Search for the Neutron Electric Dipole Moment

A cryogenic apparatus is described that enables a new experiment, nEDM@SNS, with a major improvement in sensitivity compared to the existing limit in the search for a neutron Electric Dipole Moment (EDM). It uses superfluid $^4$He to produce a high density of Ultra-Cold Neutrons (UCN) which are contained in a suitably coated pair of measurement cells. The experiment, to be operated at the Spallation Neutron Source at Oak Ridge National Laboratory, uses polarized $^3$He from an Atomic Beam Source injected into the superfluid $^4$He and transported to the measurement cells as a co-magnetometer. The superfluid $^4$He is also used as an insulating medium allowing significantly higher electric fields, compared to previous experiments, to be maintained across the measurement cells. These features provide an ultimate statistical uncertainty for the EDM of $2-3\times 10^{-28}$ e-cm, with anticipated systematic uncertainties below this level

A new variable stiffness spring using a prestressed mechanism

A novel design of a semi-active variable stiffness element is proposed, with possible applications in vibration isolation. Semi-active vibration isolators usually use variable dampers. However, it is known from the fundamental vibration theory that a variable spring can be far more effective in shifting the frequencies of the system and providing isolation. Geometry change is a common technique for building variable springs, but has disadvantages due to the complexity of the required mechanism, and slow response due to the inertia of moving parts. In the variable spring introduced here (VS), the stiffness is changed by force control in the links which corresponds to infinitesimal movements of the links, and does not need a change of geometry to provide a change of stiffness. This facilitates a fast response. The proposed VS is a simple prestressed cable mechanism with an infinitesimal mechanism. Theoretically the level of the prestress in the cables can be used to control the stiffness from zero to a maximum value that is only limited by the strength of the links. In this work, the statics, kinematics and stability of the VS are studied, the stiffness is formulated, and possible configurations of the VS are found. © 2010 by ASME

A planar neuro-musculoskeletal arm model in post-stroke patients

Mathematical modeling of the neuro-musculoskeletal system in healthy subjects has been pursued extensively. In post-stroke patients, however, such models are very primitive. Besides improving our general understanding of how stroke affects the limb motions, they can be used to evaluate rehabilitation strategies by computer simulations before clinical evaluations. A planar neuro-musculoskeletal arm model for post-stroke patients is developed. The main idea is to use a set of new coefficients, Muscle Significance Factors (MSF), to incorporate the effects of stroke in the muscle control performance. The model uses the optimal control theory to mimic the performance of the CNS and a two-link skeletal model with six muscles for the biomechanical part. The model was developed and evaluated using experimental data from six post-stroke patients with Brunnstrom levels of 4�6. The results show that MSFs are relatively distinct and independent from the arm motion which is used to determine their values. Its variation is in the range of 0�2.58 and decreases in higher Brunnstrom levels. The mean error of the model in predicting the path of motion varies from 0.9 in level 6 to 5.58 in level 4 subjects which can be considered a promising level of accuracy. Using the proposed model and the MSF to customize the model for each individual stroke patient seems a promising approach. It shows a reasonable level of robustness, i.e., independence from the type of motions and correlated with the severity of stroke, and accuracy in predicting the shape of the motion path. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature

The Effect of Mindfulness-based Cognitive Therapy on the Mental Health of Female Patients Suffering from Multiple Sclerosis

Introduction: Multiple sclersis (MS) can involve approximately all aspects of life, which leads to different problems for a person such as psychological problems. Therefore, the present study aimed to evaluate effectiveness of mindfulness-based therapy on the mental health of female patients suffering from MS. Methods: In this quasi-experimental study, the study sample consisted of 24 patients suffering from MS, who were selected via convenience sampling method. Once the participants were homogenized in regard withg their age, occupation, and education, they were devided into an experimental group (n=12) and a control group (n=12). The study instrument consisted of the general health questionnaire (GHQ-28). The experimental group attended 8 sessions&mdash;each lasting 2 hours&mdash;of training on mindfulness-based cognitive therapy, whereas the control group did not receive any interventions. In order to analyze the study data, SPSS software( ver, 22) was used via Multivariate analysis of co-variance (MANCOVA). Results: As the study results demonstrated, the difference between experimental and control groups was proved to be significant in terms of mean scores of mental health and its dimensions (p=0.0001). Conclusion: The study results supported the effectiveness of mindfulness &ndash; based cognitive therapy on mental health of female patients . It can be concluded that this method has ameliorated mental health of MS patients

A patient specific finite element simulation of intramedullary nailing to predict the displacement of the distal locking hole

Distal locking is a challenging subtask of intramedullary nailing fracture fixation due to the nail deformation that makes the proximally mounted targeting systems ineffective. A patient specific finite element model was developed, based on the QCT data of a cadaveric femur, to predict the position of the distal hole of the nail postoperatively. The mechanical interactions of femur and nail (of two sizes) during nail insertion was simulated using ABAQUS in two steps of dynamic pushing and static equilibrium, for the intact and distally fractured bone. Experiments were also performed on the same specimen to validate the simulation results. A good agreement was found between the model predictions and the experimental observations. There was a three-point contact pattern between the nail and medullary canal, only on the proximal fragment of the fractured bone. The nail deflection was much larger in the sagittal plane and increased for the larger diameter nail, as well as for more distally fractured or intact femur. The altered position of the distal hole was predicted by the model with an acceptable error (mean: 0.95; max: 1.5 mm, in different tests) to be used as the compensatory information for fine tuning of proximally mounted targeting systems. © 2018 IPE

Stiffness Oriented Tension Distribution Algorithm for Cable-Driven Parallel Robots

International audienceA novel criterion is introduced in this paper to determine the set of cable tensions for Cable-Driven Parallel Robots (CDPRs) with the aim of maximizing the robot stiffness along a specific direction. Based on the feasible polygon of the CDPR and its stiffness matrix, an algorithm selects the set of admissible cable tensions leading to the smallest moving-platform displacement, the moving-platform being subject to an external wrench. The proposed tension distribution is implemented in a control scheme and experimented on a fully-constrained CDPR for a window cleaning application