| 1. |
- Aghanavesi, Somayeh, 1981-, et al.
(författare)
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A multiple motion sensors index for motor state quantification in Parkinson's disease
- 2020
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Ingår i: Computer Methods and Programs in Biomedicine. - : Elsevier BV. - 0169-2607 .- 1872-7565. ; 189
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Tidskriftsartikel (refereegranskat)abstract
- Aim: To construct a Treatment Response Index from Multiple Sensors (TRIMS) for quantification of motor state in patients with Parkinson's disease (PD) during a single levodopa dose. Another aim was to compare TRIMS to sensor indexes derived from individual motor tasks. Method: Nineteen PD patients performed three motor tests including leg agility, pronation-supination movement of hands, and walking in a clinic while wearing inertial measurement unit sensors on their wrists and ankles. They performed the tests repeatedly before and after taking 150% of their individual oral levodopa-carbidopa equivalent morning dose.Three neurologists blinded to treatment status, viewed patients’ videos and rated their motor symptoms, dyskinesia, overall motor state based on selected items of Unified PD Rating Scale (UPDRS) part III, Dyskinesia scale, and Treatment Response Scale (TRS). To build TRIMS, out of initially 178 extracted features from upper- and lower-limbs data, 39 features were selected by stepwise regression method and were used as input to support vector machines to be mapped to mean reference TRS scores using 10-fold cross-validation method. Test-retest reliability, responsiveness to medication, and correlation to TRS as well as other UPDRS items were evaluated for TRIMS. Results: The correlation of TRIMS with TRS was 0.93. TRIMS had good test-retest reliability (ICC = 0.83). Responsiveness of the TRIMS to medication was good compared to TRS indicating its power in capturing the treatment effects. TRIMS was highly correlated to dyskinesia (R = 0.85), bradykinesia (R = 0.84) and gait (R = 0.79) UPDRS items. Correlation of sensor index from the upper-limb to TRS was 0.89. Conclusion: Using the fusion of upper- and lower-limbs sensor data to construct TRIMS provided accurate PD motor states estimation and responsive to treatment. In addition, quantification of upper-limb sensor data during walking test provided strong results. © 2019
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| 2. |
- Alves, Marco, et al.
(författare)
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Ultra-Thin and Stiff Randomly-Oriented Discontinuous Composites
- 2019
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Ingår i: Proceedings of the American Society for Composites - 34th Technical Conference, ASC 2019. - Lancaster, PA : DEStech Publications, Inc..
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 3. |
- Henningson, Måns, 1964, et al.
(författare)
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BPS partition functions in N=4 Yang-Mills theory on T-4
- 2011
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Ingår i: Journal of High Energy Physics. - : Springer Science and Business Media LLC. - 1029-8479 .- 1126-6708. ; 2011:3
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
- Hornlund, J. L., et al.
(författare)
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The weak coupling spectrum around isolated vacua in N=4 super Yang-Mills on T-3 with any gauge group
- 2008
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Ingår i: Journal of High Energy Physics. - : Springer Science and Business Media LLC. - 1029-8479 .- 1126-6708. ; 2008:7, s. 34-
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Tidskriftsartikel (refereegranskat)abstract
- The moduli space of flat connections for maximally supersymmetric Yang-Mills theories, in a space-time of the form T-3 x R, 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.
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| 5. |
- Linander, Hampus, 1985, et al.
(författare)
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(2,0) theory on circle fibrations
- 2012
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Ingår i: Journal of High Energy Physics. - 1029-8479 .- 1126-6708. ; 2012:1, s. Article Number: 159 -
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 6. |
- Memedi, Mevludin, 1983-, et al.
(författare)
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Construction of levodopa-response index from wearable sensors for quantifying Parkinson's disease motor functions
- 2016
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The goal of this study was to investigate the feasibility of wrist worn motion sensors to objectively measure motor functions in Parkinson’s disease (PD). More specifically, the aim was to construct a sensor-based levodopa-response index (SBLRI) and evaluate its clinimetric properties (convergent validity and internal consistency). Nineteen advanced PD patients and 22 healthy controls were recruited in a single center, open label, single dose clinical trial in Sweden. The subjects performed standardized motor tasks while wearing one sensor on each wrist and one on each ankle. Each sensor unit consisted of three-dimensional accelerometer and gyroscope. The patients were video recorded and the videos were blindly rated by three independent movement disorder specialists. The clinical scores were given using the Treatment Response Scale (TRS) on a scale from -3 = ‘Very Off’ to 0 = ‘On’ to +3 = ‘Very dyskinetic’. The clinical assessments were based on the overall motor function of the patients. A mean TRS was defined as the mean of the three specialists’ assessments per time point. The measurements were repeated over several time points following a single levodopa/carbidopa morning dose (50% over normal to induce dyskinesias). Sensor measurements during rapid alternating movements of hands were processed with time series analysis methods to calculate spatiotemporal parameters designed to measure bradykinesia and dyskinesia. For each hand, 96 spatiotemporal parameters were calculated and their average scores were then used in a principal component analysis to reduce the dimensionality by retaining 6 principal components. These components were then used as predictors to support vector machines and to be mapped to the mean TRS ratings of the three specialists and to calculate the SBLRI. For this analysis, a 10-fold stratified cross-validation was performed. The SBLRI was strongly correlated to mean TRS with a Pearson correlation coefficient of 0.79 (CI: 0.74-0.83, p<0.001). The 95% confidence interval for the mean squared error of SBLRI on patients data was ± 1.62 with a mean value of 0.57 whereas on healthy controls data was ± 1 with a mean value of 0.27. The sensor-based spatiotemporal parameters had good internal consistency with a Cronbach’s Alpha coefficient of 0.87 and significantly differed between patients and healthy controls. The results demonstrated that the SBLRI had good clinimetric properties for measuring motor functions (Off and dyskinesia) in PD patients. The method could also distinguish hand rotation movements exhibited by patients from those exhibited by healthy controls. The SBLRI provides effect-time profiles, which could be useful during therapy individualization of advanced PD patients.
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| 7. |
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| 8. |
- Ohlsson, Fredrik, 1983
(författare)
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Finite energy shifts in SU(n) supersymmetric Yang-Mills theory on T3 X R at weak coupling
- 2010
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Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 2470-0010 .- 2470-0029. ; 81:12
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 9. |
- Ohlsson, Fredrik, 1983, et al.
(författare)
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Geometrical nonlinearities and shape effects in electromechanical models of piezoelectric bridge structures
- 2021
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Ingår i: International Journal of Energy and Environmental Engineering. - : Springer Science and Business Media Deutschland GmbH. - 2008-9163 .- 2251-6832. ; 12, s. 725-
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Tidskriftsartikel (refereegranskat)abstract
- 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. © 2021, The Author(s).
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| 10. |
- Ohlsson, Fredrik, 1983
(författare)
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Maximally Supersymmetric Models in Four and Six Dimensions
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- We consider two examples of maximally supersymmetric models; the N=4 Yang-Mills theory in four dimensions and the (2,0) theory in six dimensions. The first part of the thesis serves as an introduction to the topics covered in the appended research papers, and begins with a self-contained discussion of principal fibre bundles and symplectic geometry. These two topics in differential geometry find applications throughout the thesis in terms of gauge theory and canonical quantization.Subsequently, we consider the N=4 supersymmetry algebra and the massless Yang-Mills multiplet representation. In particular, we discuss the vacuum structure of the N=4 theory in a space-time with the geometry of a torus, and the computation of its weak coupling spectrum. We investigate the case with a gauge group of adjoint form and discuss the implications of non-trivial bundle topology for the moduli space of flat connections. Furthermore, we consider gauging the R-symmetry of the theory by introducing a corresponding background connection. We identify a special class of terms in the partition function, which are BPS and can (in principle) be computed at weak coupling, and discuss the action of S-duality on this sector.Finally, we consider the (2,0) theory in six dimensions, provide a general introduction and derive the free tensor multiplet representation of the supersymmetry algebra. We then proceed to study (2,0) theory defined on a manifold which can be described as a circle fibred over some five-dimensional manifold. We discuss the dimensional reduction of the free (2,0) tensor multiplet on the circle and derive the (maximally supersymmetric) abelian Yang-Mills theory obtained in five dimensions for the most general metric of such a fibration. We discuss the properties of the Yang-Mills theory corresponding to the superconformal symmetry of the (2,0) theory and propose a generalization to the interacting (non-abelian) case, where a field theory description in six dimensions is problematic. The case when the circle fibration description becomes singular is also considered and we give a concrete example of such a manifold and discuss the degrees of freedom located at the singularity.
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