Search

Abstract Background Mitral regurgitation is a frequent valvular disease, with an increasing prevalence. We analysed the long-term outcomes of mitral valve repair procedures conducted over the last 10 years in our clinic using almost exclusively two different annuloplasty ring types. Methods A single-centre, retrospective analysis of mitral valve surgeries conducted between January 2005 and December 2015 for patients undergoing first-line mitral valve repair with either open (Cosgrove) or closed (CE Physio / Physio II) annuloplasty (OA or CA, respectively) rings. Results In total, 1120 patient documentations were available of which 528 underwent OA and 592 patients CA. The median age of patients was 64.0 years and 41.1% were female. The majority of these patients underwent the procedure because of degenerative valve disease. Rates of successful repair were about 90%, 72 h procedural mortality was 0.6% and the rate of re-intervention was 0.6% within the first 30 days. Functional (mitral regurgitation, left ventricular ejection fraction, left ventricular end-diastolic and systolic diameter and New York Heart Association class) as well as hard outcomes were comparable. 77.7 and 74.4% of patients were alive at the 10-year follow-up in the OA and CA groups, respectively. Upon multivariable adjustment, the hazard ratio was 0.926 (95% CI: 0.642–1.3135; p = 0.681). Conclusions The functional outcome and survival rates up to 10 years after mitral valve repair were comparable using open and closed annuloplasty rings. Whether this means these rings are interchangeable or a carefully selection of the best-for-the-patient devices will be subject of future investigations.

Background: Mitral regurgitation is a frequent valvular disease, with an increasing prevalence. We analysed the long-term outcomes of mitral valve repair procedures conducted over the last 10 years in our clinic using almost exclusively two different annuloplasty ring types.Methods: A single-centre, retrospective analysis of mitral valve surgeries conducted between January 2005 and December 2015 for patients undergoing first-line mitral valve repair with either open (Cosgrove) or closed (CE Physio / Physio II) annuloplasty (OA or CA, respectively) rings.Results: In total, 1120 patient documentations were available of which 528 underwent OA and 592 patients CA. The median age of patients was 64.0 years and 41.1% were female. The majority of these patients underwent the procedure because of degenerative valve disease. Rates of successful repair were about 90%, 72 h procedural mortality was 0.6% and the rate of re-intervention was 0.6% within the first 30 days. Functional (mitral regurgitation, left ventricular ejection fraction, left ventricular end-diastolic and systolic diameter and New York Heart Association class) as well as hard outcomes were comparable. 77.7 and 74.4% of patients were alive at the 10-year follow-up in the OA and CA groups, respectively. Upon multivariable adjustment, the hazard ratio was 0.926 (95% CI: 0.642-1.3135; p = 0.681).Conclusions: The functional outcome and survival rates up to 10 years after mitral valve repair were comparable using open and closed annuloplasty rings. Whether this means these rings are interchangeable or a carefully selection of the best-for-the-patient devices will be subject of future investigations. [ABSTRACT FROM AUTHOR]

In this paper, a compound multimode printed loop antenna based on degraded spilt-ring resonators (SRRs) for broadband wireless applications is proposed. The proposed antenna consists of an outer split ring and one inner closed ring with a big difference in size, which can be considered as degraded SRRs. By virtue of the orthogonal radiating mode of two rings, the compound multimode loop antenna can achieve multi-band resonances. Collaborating with the two coupled rings, a parasitic strip is placed close to the feed gap of the inner ring, which not only induces a new resonant frequency at upper band but also greatly improves the impedance matching in all high-frequency bands. The proposed antenna not only covers the first split ring mode at 816 MHz but also exhibits a broadband property covering from 2.3 to 4.6 GHz (reflection coefficient |S11| 0 x 0.11λ0 (λ0 is the wavelength at the lowest operating frequency), uniplanar and simple printed structure and wide bandwidth characteristics make it suitable for a wide range of wireless applications.

In this paper large connected vehicle systems are analyzed where vehicles utilize vehicle-to-vehicle (V2V) communication to control their longitudinal motion. It is shown that packet drops in communication channels introduce stochastic delay variations in the feedback loops. Scalable methods are developed to evaluate stability and disturbance attenuation while utilizing the mean, second moment, and covariance dynamics in open chain and closed ring configurations. The stability results are summarized using stability diagrams in the plane of the control parameters while varying the packet delivery ratio and the number of vehicles. Also, the relationship between the stability of different configurations is characterized. The results emphasize the feasibility of V2V communication-based control in improving traffic flow. [ABSTRACT FROM AUTHOR]

Post-buckling and collapse phenomenon of a thick closed ring subjected to external pressure on its outer surface is analyzed in this research. Ring is made of a linearly elastic polar orthotropic material. Constitutive law of linear elasticity under plane stress conditions is used. Virtual work principle is implemented to obtain the governing equations. Unlike the available noncompressible ring theories, a two-dimensional elasticity solution including the complete nonlinear Green strain field is used. The finite element method is used to solve the highly nonlinear coupled equilibrium equations. The well-known Newton-Raphson iterative technique is applied to the matrix representation of the equilibrium equations to trace the post-buckling response of the ring up to the collapse point where two antipodal points on the interior side of the ring are collided with each other. It is shown that, including the complete Green strain field is necessary in accurate estimation of the post-buckling path, especially for higher load levels and collapse load. Furthermore, orthotropic rings under external pressure load follow the bifurcation type of buckling accompanied with a stable post-buckling path. [ABSTRACT FROM AUTHOR]

Buckling and post-buckling behaviors of a moderately thick closed ring made of a through-the-thickness functionally graded material (FGM) is investigated in this research. It is assumed that material properties of the ring are distributed across the thickness in terms of a power law model. The first order theory of shear deformable rings along with the von Kármán type of geometrical non-linearity is incorporated with the virtual displacements principle to establish the complete form of the coupled non-linear equilibrium conditions. The analysis is restricted to the case of hydrostatic pressure. An exact closed-form solution is developed to trace the pre-buckling deformations of the ring. Non-linear adjacent equilibrium criterion, which is an efficient criterion to deduce the post-buckling path, is implemented to establish the highly non-linear coupled stability equations. The generalized differential quadrature (GDQ) method is adopted to discrete the equilibrium equations and the associated boundary conditions. Numerical illustrations cover the post-buckled shape and deflection of the ring in the intermediate post-buckling regime. It is shown that, unlike the case of the flat beams, response of closed FGM rings is similar to the case of isotropic homogeneous ring. Consequently, hydrostatically loaded FGM rings exhibit the imperfection insensitivity feature through the loading process. [ABSTRACT FROM AUTHOR]

A hydraulic piston assembly fractured while in service. The fracture involved a clevis assembled to the end of the cylinder piston rod. In fact, there were two fractures: one where a threaded end on the clevis was assembled to the piston rod and a second involving a fracture through the wall of the clevis. Analysis by plant personnel suggested that the stresses involved were small and that fracture should not have been expected. As a more detailed stress analysis of the clevis ring demonstrated, the stresses associated with the clevis, treated as a closed ring, were more than sufficient to have resulted in the fracture through the clevis wall. The other fracture, the fracture at the point of assembly to the piston rod, was proved to be secondary. Stress analysis as well as fracture analysis proved the point and allowed appropriate recommendations to be made to avoid a reoccurrence. [ABSTRACT FROM AUTHOR]