The tibio-femoral joint line : what is the biomechanical and clinical effect of surgical modifications?

status: publishe

Deformable microsystem for in situ cure degree monitoring of GFRP(Glass Fibre Reinforced Plastic)

Fibre Reinforced Polymer (FRP) is becoming a valid alternative to many traditional heavy metal industries because of its high specific stiffness over the more classical construction metals. Recent trend of more complex geometry of composites is causing increasing difficulty in composite manufacturing. A method to optimize the manufacturing process is thus imposed to ensure and improve the quality of manufactured parts. Because of the irregular 3D shapes of the composites, traditional flat sensor system is becoming unfavorable and nonpractical for monitoring purpose. In this work, the current development status of a deformable microsystem for in situ cure degree monitoring of a glass fibre reinforced plastic is presented. To accommodate the non-flat shape of the composites, the proposal is to interconnect non-deformable functional island, which contains the capacitive sensor for cure degree monitoring, with meander-shaped deformable interconnections. The developed sensor system is able to withstand the manufacturing process where change of pressure and internal strain, thus force exerted on the sensor system, is involved

Caring for migrants and refugees with end-stage kidney disease in Europe

With the number of migrants and refugees increasing globally, the nephrology community is increasingly confronted with issues relating to the management of end-stage kidney disease in this population, including medical, logistical, financial, and moral-ethical questions. Beginning with data for the state of affairs regarding refugees in Europe and grounded in moral reasoning theory, this Policy Forum Perspective contends that to improve care for this specific population, there is a need for: (1) clear demarcations of responsibilities across the societal (macro), local (meso), and individual (micro) levels, such that individual providers are aware of available resources and able to provide essential medical care while societies and local communities determine the general approach to dialysis care for refugees; (2) additional data and evidence to facilitate decision making based on facts rather than emotions; and (3) better information and education in a broad sense (cultural sensitivity, legal rights and obligations, and medical knowledge) to address specific needs in this population. Although the nephrology community cannot leverage a change in the geopolitical framework, we are in a position to generate accurate data describing the dimensions of care of refugee or migrant patients with end-stage kidney disease to advocate for a holistic approach to treatment for this unique patient population

Digital image correlation as a tool for three-dimensional strain analysis in human tendon tissue

BACKGROUND: Determining the mechanical behaviour of tendon and ligamentous tissue remains challenging, as it is anisotropic, non-linear and inhomogeneous in nature. METHODS: In this study, three-dimensional (3D) digital image correlation (DIC) was adopted to examine the strain distribution in the human Achilles tendon. Therefore, 6 fresh frozen human Achilles tendon specimens were mounted in a custom made rig for uni-axial loading. 3D DIC measurements of each loading position were obtained and compared to 2 linear variable differential transformers (LVDT’s). RESULTS: 3D DIC was able to calculate tendon strain in every region of all obtained images. The scatter was found to be low in all specimens and comparable to that obtained in steel applications. The accuracy of the 3D DIC measurement was higher in the centre of the specimen where scatter values around 0.03% strain were obtained. The overall scatter remained below 0.3% in all specimens. The spatial resolution of 3D DIC on human tendon tissue was found to be 0.1 mm(2). The correlation coefficient between the 3D DIC measurements and the LVDT measurements showed an excellent linear agreement in all specimens (R(2) = 0.99). Apart from the longitudinal strain component, an important transverse strain component was revealed in all specimens. The strain distribution of both components was of a strongly inhomogeneous nature, both within the same specimen and amongst different specimens. CONCLUSION: DIC proved to be a very accurate and reproducible tool for 3D strain analysis in human tendon tissue. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s40634-014-0007-8) contains supplementary material, which is available to authorized users

Internal strain monitoring in composite materials with embedded photonic crystal fiber Bragg gratings

The possibility of embedding optical fiber sensors inside carbon fiber reinforced polymer (CFRP) for structural health monitoring purposes has already been demonstrated previously. So far however, these sensors only allowed axial strain measurements because of their low sensitivity for strain in the direction perpendicular to the optical fiber's axis. The design flexibility provided by novel photonic crystal fiber (PCF) technology now allows developing dedicated fibers with substantially enhanced sensitivity to such transverse loads. We exploited that flexibility and we developed a PCF that, when equipped with a fiber Bragg grating (FBG), leads to a sensor that allows measuring transverse strains in reinforced composite materials, with an order of magnitude increase of the sensitivity over the state-of-the-art. In addition it allows shear strain sensing in adhesive bonds, which are used in composite repair patches. This is confirmed both with experiments and finite element simulations on such fibers embedded in CFRP coupons and adhesive bonds. Our sensor brings the achievable transverse strain measurement resolution close to a target value of 1 mu strain and could therefore play an important role for multi-dimensional strain sensing, not only in the domain of structural health monitoring, but also in the field of composite material production monitoring. Our results thereby illustrate the added value that PCFs have to offer for internal strain measurements inside composite materials and structures

Microstructured optical fiber Bragg grating-based shear stress sensing in adhesive bonds

We present shear stress sensing with a Bragg grating sensor fabricated in a highly birefringent microstructured optical fiber. This sensor has a shear strain sensing resolution of 0.04 pm/mu epsilon when embedded in a shear loaded adhesive bond. We achieve discrete shear stress mapping in an adhesive bond by embedding a multitude of these sensors at different locations in the bond line. Experiments and numerical modeling show the limited influence of angular misalignment of the sensor on its shear stress response. Finally, we discuss the cross-sensitivity of this sensor to shear strain and temperature

Fiber Bragg grating-based shear strain sensors for adhesive bond monitoring

The application of shear stress sensors in structural health monitoring remains limited because current sensors are either difficult to implement, they feature a low measurement resolution or the interrogation of the output signal is complex. We propose to use fiber Bragg grating-based sensors fabricated in dedicated highly birefringent microstructured optical fibers. When embedded in a host material, the orientation angle of the fiber should be chosen such that their polarization axes are aligned parallel with the direction of maximum shear stress when the host is mechanically loaded. We present experimental results of sensors embedded in the adhesive layer of single lap and double lap structural joints. These tests demonstrate that when the joints are tension loaded, the embedded sensors have a shear stress sensitivity of around 60 pm/MPa. We study the influence of the adhesive material on the sensor response, as well as the influence of sensor orientation and location in the bond line Finally, we demonstrate the minimal thermal cross-sensitivity of the shear stress sensitivity of this sensor

Microstructured Optical Fiber Sensors Embedded in a Laminate Composite for Smart Material Applications

Fiber Bragg gratings written in highly birefringent microstructured optical fiber with a dedicated design are embedded in a composite fiber-reinforced polymer. The Bragg peak wavelength shifts are measured under controlled axial and transversal strain and during thermal cycling of the composite sample. We obtain a sensitivity to transversal strain that exceeds values reported earlier in literature by one order of magnitude. Our results evidence the relevance of using microstructured optical fibers for structural integrity monitoring of composite material structures