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In this paper we present a novel concept to efficiently harvest vibrational energy at low frequencies and very small displacement. We describe and evaluate an electromagnetic energy harvester which generates power from a magnetic circuit with motion induced variations of an air gap. External vibrations induce oscillations of the gap length around an equilibrium point, due to a linear spring counteracting the magnetic force. The relative position of the spring can be adjusted to optimize the harvester output for excitation amplitude and frequency. A simulation model is built in COMSOL and verified by comparison with lab measurements. The simulation model is used to determine the potential performance of the proposed concept under both harmonic and non-harmonic excitation. Under harmonic excitation, we achieve a simulated RMS load power of 26.5 μW at 22 Hz and 0.028 g acceleration amplitude. From a set of comparable EH we achieve the highest theoretical power metric of 1712.2 µW/cm3/g2 while maintaining the largest relative bandwidth of 81.8%. Using measured non-harmonic vibration data, with a mean acceleration of 0.039 g, resulted in a mean power of 52 μW. Moreover, the simplicity and robustness of our design makes it a competitive alternative for use in practical situations.

Objective To determine to what extent accelerometer-based arm, leg and trunk activity is associated with sensorimotor impairments, walking capacity and other factors in subacute stroke. Design Cross-sectional study. Patients Twenty-six individuals with stroke (mean age 55.4 years, severe to mild motor impairment). Methods Data on daytime activity were collected over a period of 4 days from accelerometers placed on the wrists, ankles and trunk. A forward stepwise linear regression was used to determine associations between free-living activity, clinical and demographic variables. Results Arm motor impairment (Fugl-Meyer Assessment) and walking speed explained more than 60% of the variance in daytime activity of the more-affected arm, while walking speed alone explained 60% of the more-affected leg activity. Activity of the less-affected arm and leg was associated with arm motor impairment (R2 = 0.40) and independence in walking (R2 = 0.59). Arm activity ratio was associated with arm impairment (R2 = 0.63) and leg activity ratio with leg impairment (R2 = 0.38) and walking speed (R2 = 0.27). Walking-related variables explained approximately 30% of the variance in trunk activity. Conclusion Accelerometer-based free-living activity is dependent on motor impairment and walking capacity. The most relevant activity data were obtained from more-affected limbs. Motor impairment and walking speed can provide some information about real-life daytime activity levels.

We consider nonlinear shape effects appearing in the lumped electromechanical model of a bimorph piezoelectric bridge structure due to the interaction between the electromechanical constitutive model and the geometry of the structure. At finite proof-mass displacement and electrode voltage, the shape of the beams is no longer given by Euler-Bernoulli theory which implies that shape effects enter in both the electrical and mechanical domains and in the coupling between them. Accounting for such effects is important for the accurate modelling of, e.g., piezoelectrical energy harvesters and actuators in the regime of large deflections and voltages. We present a general method, based on a variational approach minimizing the Gibbs enthalpy of the system, for computing corrections to the nominal shape function and the associated corrections to the lumped model. The lowest order correction is derived explicitly and is shown to produce significant improvements in model accuracy, both in terms of the Gibbs enthalpy and the shape function itself, over a large range of displacements and voltages. Furthermore, we validate the theoretical model using large deflection finite element simulations of the bridge structure and conclude that the lowest order correction substantially improve the model, obtaining a level of accuracy expected to be sufficient for most applications. Finally, we derive the equations of motion for the lowest order corrected model and show how the coupling between the electromechanical properties and the geometry of the bridge structure introduces nonlinear interaction terms.

Understanding the complex interactions of biochemical processes underlying human disease represents the holy grail of systems biology. When processes are modelled in ordinary differential equation (ODE) fashion, the most common tool for their analysis is linear stability analysis where the long-term behaviour of the model is determined by linearizing the system around its steady states. However, this asymptotic behaviour is often insufficient for completely determining the structure of the underlying system. A complementary technique for analysing a system of ODEs is to consider the set of symmetries of its solutions. Symmetries provide a powerful concept for the development of mechanistic models by describing structures corresponding to the underlying dynamics of biological systems. To demonstrate their capability, we consider symmetries of the nonlinear Hill model describing enzymatic reaction kinetics and derive a class of symmetry transformations for each order of the model. We consider a minimal example consisting of the application of symmetry-based methods to a model selection problem, where we are able to demonstrate superior performance compared to ordinary residual-based model selection. Moreover, we demonstrate that symmetries reveal the intrinsic properties of a system of interest based on a single time series. Finally, we show and propose that symmetry-based methodology should be considered as the first step in a systematic model building and in the case when multiple time series are available it should complement the commonly used statistical methodologies.

A discerning cyclist requires a bike that is light, stiff, and fast, yet comfortable. In partnering with TeXtreme ® on the new Ultravox SSL road bike, SwiftCarbon has achieved its greatest strength-to-weight ratio frame yet. TeXtreme ® Spread Tow carbon reinforcements are an innovative type of composite reinforcement employed to reduce weight, increase performance, and provide better surface smoothness in advanced composites.

Background Motor function assessments with rating scales in relation to the pharmacokinetics of levodopa may increase the understanding of how to individualize and fine-tune treatments. Objectives This study aimed to investigate the pharmacokinetic profiles of levodopa-carbidopa and the motor function following a single-dose microtablet administration in Parkinson’s disease. Methods This was a single-center, open-label, single-dose study in 19 patients experiencing motor fluctuations. Patients received 150% of their individual levodopa equivalent morning dose in levodopa-carbidopa microtablets. Blood samples were collected at pre-specified time points. Patients were video recorded and motor function was assessed with six UPDRS part III motor items, dyskinesia score, and the treatment response scale (TRS), rated by three blinded movement disorder specialists. Results AUC0–4/dose and C max/dose for levodopa was found to be higher in Parkinson’s disease patients compared with healthy subjects from a previous study, (p = 0.0008 and p = 0.026, respectively). The mean time to maximum improvement in sum of six UPDRS items score was 78 min (±59) (n = 16), and the mean time to TRS score maximum effect was 54 min (±51) (n = 15). Mean time to onset of dyskinesia was 41 min (±38) (n = 13). Conclusions In the PD population, following levodopa/carbidopa microtablet administration in fasting state, the Cmax and AUC0–4/dose were found to be higher compared with results from a previous study in young, healthy subjects. A large between subject variability in response and duration of effect was observed, highlighting the importance of a continuous and individual assessment of motor function in order to optimize treatment effect.

Objective: To determine whether there are differences in arm, leg and trunk activity measured by acceleration between weekdays and weekends in people undergoing rehabilitation in the subacute stage after stroke. Design: Cross-sectional study. Patients: Twenty-eight individuals with stroke (mean age 55.4 years; severe to mild impairment) and 10 healthy controls. Methods: A set of 5 3-axial accelerometers were used on the trunk, wrists and ankles during 2 48-h sessions at weekdays and over a weekend. Day-time acceleration raw data were expressed as the signal magnitude area. Asymmetry between the affected and less-affected limb was calculated as a ratio. Results: Participants with stroke used their both arms and legs less at weekends than on weekdays (p

Background In neurology and rehabilitation the primary interest for using wearables is to supplement traditional patient assessment and monitoring in hospital settings with continuous data collection at home and in community settings. The aim of this project was to develop a novel wearable garment with integrated sensors designed for continuous monitoring of physiological and movement related variables to evaluate progression, tailor treatments and improve diagnosis in epilepsy, Parkinson’s disease and stroke. Methods In this paper the early development and evaluation of a prototype designed to monitor movements and heart rate is described. An iterative development process and evaluation of an upper body garment with integrated sensors included: identification of user needs, specification of technical and garment requirements, garment development and production as well as evaluation of garment design, functionality and usability. The project is a multidisciplinary collaboration with experts from medical, engineering, textile, and material science within the wearITmed consortium. The work was organized in regular meetings, task groups and hands-on workshops. User needs were identified using results from a mixed-methods systematic review, a focus group study and expert groups. Usability was evaluated in 19 individuals (13 controls, 6 patients with Parkinson’s disease) using semi-structured interviews and qualitative content analysis. Results The garment was well accepted by the users regarding design and comfort, although the users were cautious about the technology and suggested improvements. All electronic components passed a washability test. The most robust data was obtained from accelerometer and gyroscope sensors while the electrodes for heart rate registration were sensitive to motion artefacts. The algorithm development within the wearITmed consortium has shown promising results. Conclusions The prototype was accepted by the users. Technical improvements are needed, but preliminary data indicate that the garment has potential to be used as a tool for diagnosis and treatment selection and could provide added value for monitoring seizures in epilepsy, fluctuations in PD and activity levels in stroke. Future work aims to improve the prototype further, develop algorithms, and evaluate the functionality and usability in targeted patient groups. The potential of incorporating blood pressure and heart-rate variability monitoring will also be explored.

A treatment response objective index (TRIS) was previously developed based on sensor data from pronation-supination tests. This study aimed to examine the performance of TRIS for medication effects in a new population sample with Parkinson's disease (PD) and its usefulness for constructing individual dose-response models.Twenty-five patients with PD performed a series of tasks throughout a levodopa challenge while wearing sensors. TRIS was used to determine motor changes in pronation-supination tests following a single levodopa dose, and was compared to clinical ratings including the Treatment Response Scale (TRS) and six sub-items of the UPDRS part III.As expected, correlations between TRIS and clinical ratings were lower in the new population than in the initial study. TRIS was still significantly correlated to TRS (rThe objective sensor index shows promise for constructing individual dose-response models, but further evaluations and retraining of the TRIS algorithm are desirable to improve its performance and to ensure its clinical effectiveness.

Purpose The aim of this prospective, video-electroencephalography (video-EEG) controlled study was to evaluate the performance of an accelerometry-based wearable system to detect tonic-clonic seizures (TCSs) and to investigate the accuracy of different seizure detection algorithms using separate training and test data sets. Methods Seventy-five epilepsy surgery candidates undergoing video-EEG monitoring were included. The patients wore one three-axis accelerometer on each wrist during video-EEG. The accelerometer data was band-pass filtered and reduced using a movement threshold and mapped to a time-frequency feature space representation. Algorithms based on standard binary classifiers combined with a TCS specific event detection layer were developed and trained using the training set. Their performance was evaluated in terms of sensitivity and false positive (FP) rate using the test set. Results Thirty-seven available TCSs in 11 patients were recorded and the data was divided into disjoint training (27 TCSs, three patients) and test (10 TCSs, eight patients) data sets. The classification algorithms evaluated were K-nearest-neighbors (KNN), random forest (RF) and a linear kernel support vector machine (SVM). For the TCSs detection performance of the three algorithms in the test set, the highest sensitivity was obtained for KNN (100% sensitivity, 0.05 FP/h) and the lowest FP rate was obtained for RF (90% sensitivity, 0.01 FP/h). Conclusions The low FP rate enhances the clinical utility of the detection system for long-term reliable seizure monitoring. It also allows a possible implementation of an automated TCS detection in free-living environment, which could contribute to ascertain seizure frequency and thereby better seizure management.

Using current battery technology the life-time of a leadless pacemaker is approximately 6-10 years, with a large portion of the pacemaker occupied by the battery. This paper investigates the possibility to use a MEMS piezoelectric harvester as a complementary energy source in leadless pacemakers. The challenge is to combine the low resonance frequency required to harvest energy from a heartbeat with the small volume of 20×4×3 mm3 available, with the corresponding harvester displacement restricted to 2 mm. Due to the displacement restriction the selected structure was a double clamped bridge in order to reduce the mass displacement, with various meander-type designs simulated to reduce resonance frequency. To further reduce resonance frequency large proof-masses of tungsten were attached by gluing. Two types of tungsten proof-masses were added to four different harvesters, 16.4 mg and 16.6 mg on sample 1 and 2 and 502 mg and 492 mg proof-mass on sample 3 and 4. The structures have 2 µm patterned PZT (deposited by sol-gel technique) and Pt metal electrodes for d31 mode harvesting. The power output measured from one of the two PZT/electrodes was 0.13 nW with 50 µm deflection at 100 k Ω optimal load resistance and 9.1 mVpp at 232 Hz.

The quality factor of a packaged MEMS resonating structure depends on both the packaging pressure and the structure’s proximity to the walls. This type of mechanical constraints, which causes energy dissipation from the structure to the surrounding air, are applicable for oscillating energy harvesters and should be considered in the design process. However, the modelling of energy losses or the measurements of their direct influence inside a packaged chip is not trivial. In this paper, a simple experimental method to quantify the energy loss in an oscillating MEMS structures due to the surrounding air is described together with preliminary results. The main advantage of the method is the ability to characterize the damping contributions under different vacuum and packaging conditions without requiring any packaging of the harvester chip or fabrication of multiple devices with different cavity depths.

In Part 1 of this two-part article Fredrik Ohlsson of Oxeon AB outlined the construction and manufacture of spread tow reinforcements and discussed their benefits over other reinforcements. In Part 2 he looks at their design possibilities, and provides some case studies.

Spread-tow carbon reinforcements are a new kind of composite reinforcement which is suitable for saving weight. The spread-tow structure makes it possible to achieve thinner laminates. Straighter fibres with reduced crimp optimize and strengthen the composite. Fewer crimps reduce the amount of excess plastic, thereby minimizing weight. This chapter looks at some existing customer cases from both the Formula 1 and the aerospace sectors in which this new technology has contributed to substantial weight savings.

People after stroke have difficulties to reach sufficient physical activity level during their rehabilitation and particularly outside the therapy time. We aim to quantify activity levels and investigate differences in motor activity in weekdays and weekends in a subacute stage after stroke. Data from multiple three-axis accelerometers was collected during two 48 h sessions in 11 patients. The activity level and symmetry indices were sensitive to variations in weekend and weekdays. This information is valuable in rehabilitation planning and management and enables identification of those in risk of low physical activity and inactivity.

The shape of a doubly clamped bridge structure depends on its deflection. At large deflections, where the system exhibits nonlinear behaviour, the shape effect becomes significant. We present a general method, based on variational analysis, for computing corrections to the nominal linear regime shape function. The method is used to compute the first non-trivial correction and quantify the corresponding improvement in the large deflection regime. The model obtained is also validated using FEM simulations.

During the manufacturing of MEMS components, slanted beams can be produced in the etching process. We show that this can be used to produce skew motion that causes deflection of a proof mass out of the device plane also when the excitation is confined to the device plane. This allows construction of an energy harvester that uses a planar manufacturing process and produces power also with in-plane excitation. To obtain this with traditional methods it would be necessary to manufacture separate components and then mount them with their sensitive axes orthogonal to each other.

We consider (2,0) theory on a manifold M_6 that is a fibration of a spatial S^1 over some five-dimensional base manifold M_5. Initially, we study the free (2,0) tensor multiplet which can be described in terms of classical equations of motion in six dimensions. Given a metric on M_6 the low energy effective theory obtained through dimensional reduction on the circle is a Maxwell theory on M_5. The parameters describing the local geometry of the fibration are interpreted respectively as the metric on M_5, a non-dynamical U(1) gauge field and the coupling strength of the resulting low energy Maxwell theory. We derive the general form of the action of the Maxwell theory by integrating the reduced equations of motion, and consider the symmetries of this theory originating from the superconformal symmetry in six dimensions. Subsequently, we consider a non-abelian generalization of the Maxwell theory on M_5. Completing the theory with Yukawa and phi^4 terms, and suitably modifying the supersymmetry transformations, we obtain a supersymmetric Yang-Mills theory which includes terms related to the geometry of the fibration., Comment: 24 pages, v2 References added, typos corrected

We consider N = 4 Yang-Mills theory on a flat four-torus with the R-symmetry current coupled to a flat background connection. The partition function depends on the coupling constant of the theory, but when it is expanded in a power series in the R-symmetry connection around the loci at which one of the supersymmetries is unbroken, the constant and linear terms are in fact independent of the coupling constant and can be computed at weak coupling for all non-trivial 't Hooft fluxes. The case of a trivial 't Hooft flux is difficult because of infrared problems, but the corresponding terms in the partition function are uniquely determined by S-duality., Comment: 23 pages, v2 Minor corrections

We consider a perturbative treatment, in the regime of weak gauge coupling, of supersymmetric Yang-Mills theory in a space-time of the form T-3 X R with SU(n)/Z(n) gauge group and a nontrivial gauge bundle. More specifically, we consider the theories obtained as power series expansions around a certain class of normalizable vacua of the classical theory, corresponding to isolated points in the moduli space of flat connections, and the perturbative corrections to the free energy eigenstates and eigenvalues in the weakly interacting theory. The perturbation theory construction of the interacting Hilbert space is complicated by the divergence of the norm of the interacting states. Consequently, the free and interacting Hilbert spaces furnish unitarily inequivalent representations of the algebra of creation and annihilation operators of the quantum theory. We discuss a consistent redefinition of the Hilbert space norm to obtain the interacting Hilbert space and the properties of the interacting representation. In particular, we consider the lowest nonvanishing corrections to the free energy spectrum and discuss the crucial importance of supersymmetry for these corrections to be finite.

The moduli space of flat connections for maximally supersymmetric Yang-Mills theories, in a space-time of the form T^3xR, contains isolated points, corresponding to normalizable zero energy states, for certain simple gauge groups G. We consider the low energy effective field theories in the weak coupling limit supported on such isolated points and find that when quantized they consist of an infinite set of harmonic oscillators whose angular frequencies are completely determined by the Lie algebra of G. We then proceed to find the isolated flat connections for all simple G and subsequently specify the corresponding effective field theories., Comment: 32 pages, 11 figures, v4 Added chapter, Published version

Aim: This 4-week open-label observational study describes the effect of introducing a microtablet dose dispenser and adjusting doses based on objective free-living motor symptom monitoring in individuals with Parkinson's disease (PD). Methods: Twenty-eight outpatients with PD on stable levodopa treatment with dose intervals of ≤4 hour had their daytime doses of levodopa replaced with levodopa/carbidopa microtablets, 5/1.25 mg (LC-5) delivered from a dose dispenser device with programmable reminders. After 2 weeks, doses were adjusted based on ambulatory accelerometry and clinical monitoring. Results: Twenty-four participants completed the study per protocol. The daily levodopa dose was increased by 15% (112 mg, P < 0.001) from period 1 to 2, and the dose interval was reduced by 12% (22 minutes, P = 0.003). The treatment adherence to LC-5 was high in both periods. The MDS-UPDRS parts II and III, disease-specific quality of life (PDQ-8), wearing-off symptoms (WOQ-19), and nonmotor symptoms (NMS Quest) improved after dose titration, but the generic quality-of-life measure EQ-5D-5L did not. Blinded expert evaluation of accelerometry results demonstrated improvement in 60% of subjects and worsening in 25%. Conclusions: The introduction of a levodopa microtablet dispenser and accelerometry aided dose adjustments improve PD symptoms and quality of life in the short term.

This paper presents experimental and numerical results for tensile strength of tow based discontinues composite (TBDC) plates manufactured using ultra-thin fibre tapes of high stiffness carbon fibres. Numerical models were used to explore the design space of these materials, in order to identify the optimal tow properties that maximise the strength of TBDCs. The experimental show good agreement with the numerical predictions and demonstrate a significant increase in the tensile strength by reducing the tow thickness and increasing the stiffness of the fibres. Strength increases of up to 100%, compared with a commercially available material system, are found, illustrating the highly promising potential of this type of material.

Conventional randomly-oriented Tow Based Discontinues Composites (TBDCs) are materials which combine good mechanical properties, lightweight and high manufacturability, and are therefore interesting for high-volume transport industries. This paper proposes, designs and successfully demonstrates a pathway to produce TBDCs with outstanding stiffness and tensile strength, by using ultra-thin tapes of (ultra-) high modulus carbon-fibres. Numerical models are used to explore the design space of discontinuous composite materials, in order to identify the optimal microstructural design to maximise stiffness and strength. Selected microstructures are manufactured and tested under tension; the experimental results show good agreement with the numerical predictions, and demonstrate a significant increase in the tensile strength and Young’s modulus of TBDCs by reducing the tow thickness and increasing the modulus of the fibres. Strength and stiffness increases of over 100% compared with the commercially available TBDC systems are achieved, resulting in mechanical properties that match the strength and overcome the stiffness of aerospace-graded continuous-fibre laminates.

The potential of impact-driven frequency up-conversion in a MEMS EH is evaluated using numerical simulations. The investigated design is compared to a conventional cantilever EH in terms of output power and loss rate. The upshifting can lead to significantly increased output power at a similar loss rate but as the time scale for the loss is long, the benefit is limited. This also requires an effective upshifting process. The design of the impact introduces a length scale that must be selected with excitation, gravity, and pre-stress taken into account. This makes this type of EH application-dependent as a non-optimal choice may result in low output power.