Background: The perioperative management of antiplatelet therapy in noncardiac surgery patients who have undergone previous percutaneous coronary intervention (PCI) remains a dilemma. Continuing dual antiplatelet therapy (DAPT) may carry a risk of bleeding, while stopping antiplatelet therapy may increase the risk of perioperative major adverse cardiovascular events (MACE). Methods: Occurrence of Bleeding and Thrombosis during Antiplatelet Therapy In Non-Cardiac Surgery (OBTAIN) was an international prospective multicentre cohort study of perioperative antiplatelet treatment, MACE, and serious bleeding in noncardiac surgery. The incidences of MACE and bleeding were compared in patients receiving DAPT, monotherapy, and no antiplatelet therapy before surgery. Unadjusted risk ratios were calculated taking monotherapy as the baseline. The adjusted risks of bleeding and MACE were compared in patients receiving monotherapy and DAPT using propensity score matching. Results: A total of 917 patients were recruited and 847 were eligible for inclusion. Ninety-six patients received no antiplatelet therapy, 526 received monotherapy with aspirin, and 225 received DAPT. Thirty-two patients suffered MACE and 22 had bleeding. The unadjusted risk ratio for MACE in patients receiving DAPT compared with monotherapy was 1.9 (0.93e3.88), P¼0.08. There was no difference in MACE between no antiplatelet treatment and monotherapy 1.03 (0.31e 3.46), P¼0.96. Bleeding was more frequent with DAPT 6.55 (2.3e17.96) P¼0.0002. In a propensity matched analysis of

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This paper addresses the axial vibrations of herringbone gears. Theoretically, herringbone gears balance their axial loads due to their symmetry; however, in practice, they present high vibrations. The reasons are manufacturing deviations such as lead angle errors, pitch error differences between each side of the gear, misalignment between pinion and gear axes, etc. These errors can be represented as an error function of sinusoidal form acting as forced vibrations over the teeth. Although axial and lateral motions of a gear pair are generally coupled, the symmetric geometry of herringbone gears makes possible to analyze the axial and lateral stiffness as uncoupled functions. It is viable then to represent the axial motion as a single degree of freedom model. The effect of each parameter of the error function is analyze individually in order to determine which has the greater effect in the system. Results are compared to field data showing good agreement.

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