Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world

Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection

Elasto-plastic stress analysis of aluminum metal matrix laminated plates with a circular hole under transverse loading

Metal-matrix composites provide new materials with superior properties. They give high strength and stiffness and fatigue properties. In this study, a stainless steel fiber reinforced aluminum metal-matrix laminated simply supported plate with a circular hole is loaded transversely. Elastic, elasto-plastic and residual stresses are calculated in the symmetric and/or antisymmetric cross-ply and angle-ply laminated plate for small deformations by using finite elements method. Load steps are chosen 200, 400 and 600. Isoparametric quadrilateral element with nine node is developed for the elasto-plastic analysis. Metal-matrix composite laminated plate is manufactured by using moulds under the action of 30 MPa and heating up 600degreesC. The first-order shear deformation theory is used in the study

An elastic-plastic stress analysis of thermoplastic composite beams loaded by bending moments

In this study, an elastic-plastic stress analysis is carried out on a high-density thermoplastic-based composite cantilever beam loaded by a bending moment at the free end. The composite beam is reinforced unidirectionally by steel fibers, at 0 degrees, 30 degrees, 45 degrees, 60 degrees and 90 degrees orientation angles. An analytical solution is performed for satisfying both the governing differential equation in the plane stress case and boundary conditions for small plastic deformations. The solution is carried out under the assumption of the Bernoulli-Navier hypotheses. It is found that the intensity of the residual stress component of sigma(x) is maximum at the upper and lower surfaces or at the boundary of the elastic and plastic regions. The composite material is assumed to be strain-hardening. The Tsai-Hill theory is used as a yield criterion. The displacement components are found in the elastic region. (C) 2000 Elsevier Science Ltd. All rights reserved

An investigation on buckling of laminated plates with central square hole

In this paper buckling analysis of rectangular composite laminates with a central square hole is investigated. Using the first order shear deformation theory, the buckling loads of rectangular laminated plates under the inplane loads are found for various hole sizes. The four-mode finite element method is used to obtain critical loads. The critical loads of symmetric angle-ply, antisymmetric cross-ply or angle-ply laminates are found for constant or various thicknesses, simple or clamped boundary conditions, various modules ratios, simple or biaxial loading versus hole sizes. Some results are compared with those of given references

Material nonlinear behavior of laminated metal-matrix composite plates supported at edges under uniform traverse loading

This paper deals with material non-linear behavior of steel fiber reinforced aluminum metal-matrix composite plates prepared by the squeeze casting process. By such an analysis it is intended to form an opinion about elastic-plastic behavior of laminated plates used in engineering problems associated with structural designs. Therefore, loads that begin plastic flow at any point of laminate for various stacking sequences are obtained. Afterwards, how further increase in loads gradually causes spreading of plastic zone is examined. Elastic/plastic and residual stress variations correspond to diverse stacking sequences of laminated plates are illustrated in figures. Plastic zone expansions are displayed in simply supported symmetric and antisymmetric laminated composite plates by contour plots. The finite element method is applied for analyses based on small deformation effects including shear deformation. For nonlinear solution of the problem a combined incremental/iterative procedure (modified Newton-Raphson) is followed and load increments are chosen to be sufficiently small to obtain a rapid-converged equilibrium state. Mechanical properties of an orthotropic layer are obtained experimentally. (C) 2002 Elsevier Science Ltd. All rights reserved

Stacking sequence effects on elastic-plastic stress variation in composite plates with clamped edges

This paper deals with stacking sequence effects on stress variation in steel fibre reinforced aluminium metal-matrix composite plates prepared by squeeze casting process. By such an analysis, it is intended to form an opinion about elastic-plastic stress variation in laminated plates used in engineering applications associated with structural designs. Load carrying capacities of laminated composite plates for various stacking sequences are examined. Elastic/plastic and residual stress variations correspond to arbitrary lay-ups are given by means of figures. Laminated composite plates are assumed to be clamped at all edges. The finite element method is applied for such an analysis considering shear deformation effects and small plastic deformations. For the nonlinear solution of the problem, a combined incremental/iterative procedure (modified Newton-Raphson) is used. Mechanical properties of an orthotropic layer are obtained experimentally