158 research outputs found
Classification of patients with knee osteoarthritis in clinical phenotypes: data from the osteoarthritis initiative
<div><p>Objectives</p><p>The existence of phenotypes has been hypothesized to explain the large heterogeneity characterizing the knee osteoarthritis. In a previous systematic review of the literature, six main phenotypes were identified: Minimal Joint Disease (MJD), Malaligned Biomechanical (MB), Chronic Pain (CP), Inflammatory (I), Metabolic Syndrome (MS) and Bone and Cartilage Metabolism (BCM). The purpose of this study was to classify a sample of individuals with knee osteoarthritis (KOA) into pre-defined groups characterized by specific variables that can be linked to different disease mechanisms, and compare these phenotypes for demographic and health outcomes.</p><p>Methods</p><p>599 patients were selected from the OAI database FNIH at 24 monthsâ time to conduct the study. For each phenotype, cut offs of key variables were identified matching the results from previous studies in the field and the data available for the sample. The selection process consisted of 3 steps. At the end of each step, the subjects classified were excluded from the further classification stages. Patients meeting the criteria for more than one phenotype were classified separately into a âcomplex KOAâ group.</p><p>Results</p><p>Phenotype allocation (including complex KOA) was successful for 84% of cases with an overlap of 20%. Disease duration was shorter in the MJD while the CP phenotype included a larger number of Women (81%). A significant effect of phenotypes on WOMAC pain (F = 16.736 p <0.001) and WOMAC physical function (F = 14.676, p < 0.001) was identified after controlling for disease duration.</p><p>Conclusion</p><p>This study signifies the feasibility of a classification of KOA subjects in distinct phenotypes based on subgroup-specific characteristics.</p></div
Derivation of dual horizon state-based peridynamics formulation based on euler-lagrange equation
The numerical solution of peridynamics equations is usually done by using uniform spatial discretisation. Although implementation of uniform discretisation is straightforward, it can increase computational time significantly for certain problems. Instead, non-uniform discretisation can be utilised and different discretisation sizes can be used at different parts of the solution domain. Moreover, the peridynamic length scale parameter, horizon, can also vary throughout the solution domain. Such a scenario requires extra attention since conservation laws must be satisfied. To deal with these issues, dual-horizon peridynamics was introduced so that both non-uniform discretisation and variable horizon sizes can be utilised. In this study, dual-horizon peridynamics formulation is derived by using EulerâLagrange equation for state-based peridynamics. Moreover, application of boundary conditions and determination of surface correction factors are also explained. Finally, the current formulation is verified by considering two benchmark problems including plate under tension and vibration of a plate
Lagrange Multipliers in Infinite-Dimensional Systems, Methods of
International audienceThis entry will describe Lagrange multipliers method using a formulation which is valid for infinite-dimensional dynamical systems. The method of Lagrange multipliers is employed to deal with systems subject to constraints. The theoretical foundations of this method are presented, and a proof of the main theorem is illustrated for the relevant case of constraints defined on a Banach vector space
Stress da radiazione RF a 900 MHz ed attivazione di elementi trasponibili in tessuti germinali di Drosophila melanogaster
Nel mondo naturale gli individui, le popolazioni e le specie si devono confrontare con variazioni delle condizioni ambientali. Gli organismi e le loro cellule mettono in atto un adattamento fisiologico attraverso risposte che sono immediate e reversibili. Condizioni di stress perĂČ, possono causare modificazioni a livello genomico che possono alterare processi biologici fondamentali conducendo a trasformazioni cellulari. Ă noto da tempo che fattori ambientali provocano condizioni di stress che possono indurre in vari organismi lâattivazione di elementi genetici mobili o elementi trasponibili (TEs) il cui movimento Ăš tra le cause di instabilitĂ genomica. In questo lavoro, individui di Drosophila melanogaster sono stati sottoposti a stress da radiazione RF a 900 MHz ed esaminati per lâattivazione di TEs nei tessuti germinali di entrambi i sessi. Tale stress ha causato un significativo incremento dellâattivazione di tali elementi, confermando che diversi stress ambientali possono avere come conseguenza lâinstabilitĂ dei genomi e la comparsa di mutazioni de novo dovute allâinserzione di elementi trasponibili in geni codificanti
Electromechanical analysis of an adaptive piezoelectric energy harvester controlled by two segmented electrodes with shunt circuit networks
This paper presents an adaptive power harvester using a shunted piezoelectric control system with segmented electrodes. This technique has spurred new capability for widening the three simultaneous resonance frequency peaks using only a single piezoelectric laminated beam where normally previous works only provide a single peak for the resonance at the first mode. The benefit of the proposed techniques is that it provides effective and robust broadband power generation for application in self-powered wireless sensor devices. The smart structure beam with proof mass offset is considered to have simultaneous combination between vibration-based power harvesting and shunt circuit control-based electrode segments. As a result, the system spurs new development of the two mathematical methods using electromechanical closed-boundary value techniques and Ritz method-based weak-form analytical approach. The two methods have been used for comparison giving accurate results. For different electrode lengths using certain parametric tuning and harvesting circuit systems, the technique enables the prediction of the power harvesting that can be further proved to identify the performance of the system using the effect of varying circuit parameters so as to visualize the frequency and time waveform responses
The effect of uncertain material properties on free vibrations of thin periodic plates
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