Turnpike Catheter failure, causes and mechanisms: Insights from the MAUDE database.

Background: The Turnpike catheters (Teleflex, Wayne, PA, USA) is a microcatheter that was approved by the Food and Drug Administration in November 2014 to be used to access discrete regions of the coronary and peripheral vasculature. Methods: The Manufacturer and User Facility Device Experience (MAUDE) database was queried for reports of the Turnpike catheters from March 2015 through August 2021. Results: A total of 216 reports were found during the study period. After excluding duplicate reports (n = 21), our final cohort included 195 reports. The most common failure mode was catheter tip break or detachment (83%, n = 165) which was significantly associated with over-torquing (p-value = 0.025). The most common clinical consequence was the entrapment of the catheter (33%, n = 65), followed by vessel injury (7.8% n = 15) and vessel occlusion (3.6%, n = 7). Most patients had no consequences (47.0%, n = 93) or recovered (11%, n = 22). A total of 4 deaths were reported. 35.8% of reports (n = 69) specified the presence of severe calcification in the target vessel. Over torquing by interventionists was reported in 33.2% of events (n = 64). Conclusion: Despite clinical trials demonstrating the safety of the Turnpike catheters, complications can still occur. These data serve to inform operators about potentional risks and complications associated with the use of the device. Physicians should avoid over-torqueing which seems to be the most common mechanism for device complications.

The promise of dawn: Microalgae photoacclimation as an optimal control problem of resource allocation.

Photosynthetic microorganisms are known to adjust their photosynthetic capacity according to light intensity. This so-called photoacclimation process is thought to maximize growth at equilibrium, but its dynamics under varying conditions remains less understood. To tackle this problem, microalgae growth and photoacclimation are represented by a (coarse-grained) resource allocation model. Using optimal control theory (the Pontryagin maximum principle) and numerical simulations, we determine the optimal strategy of resource allocation to maximize microalgal growth rate over a time horizon. We show that, after a transient, the optimal trajectory approaches the optimal steady state, a behavior known as the turnpike property. Then, a bi-level optimization problem is solved numerically to estimate model parameters from experimental data. The fitted trajectory represents well a Dunaliella tertiolecta culture facing a light down-shift. Finally, we study photoacclimation dynamics under day/night cycle. In the optimal trajectory, the synthesis of the photosynthetic apparatus surprisingly starts a few hours before dawn. This anticipatory behavior has actually been observed both in the laboratory and in the field. This shows the algal predictive capacity and the interest of our method which predicts this phenomenon.

Optimal control of the Lotka-Volterra system: turnpike property and numerical simulations.

The Lotka-Volterra model is a differential system of two coupled equations representing the interaction of two species: a prey one and a predator one. We formulate an optimal control problem adding the effect of hunting both species as the control variable. We analyse the optimal hunting problem paying special attention to the nature of the optimal state and control trajectories in long time intervals. To do that, we apply recent theoretical results on the frame to show that, when the time horizon is large enough, optimal strategies are nearly steady-state. Such path is known as turnpike property. Some experiments are performed to observe such turnpike phenomenon in the hunting problem. Based on the turnpike property, we implement a variant of the single shooting method to solve the previous optimisation problem, taking the middle of the time interval as starting point.

Language of CTO interventions - Focus on hardware.

The knowledge of variety of chronic total occlusion (CTO) hardware and the ability to use them represents the key to success of any CTO interventions. However, the multiplicity of CTO hardware and their physical character and the terminology used by experts create confusion in the mind of an average interventional cardiologist, particularly a beginner in this field. This knowledge is available but is scattered. We aim to classify and compare the currently used devices based on their properties focusing on how physical character of each device can be utilized in a specific situation, thus clarifying and simplifying the technical discourse.

On Ramsey's conjecture.

Studying a one-sector economy populated by finitely many heterogeneous households that are subject to no-borrowing constraints, we confirm a conjecture by Frank P. Ramsey according to which, in the long run, society would be divided into the set of patient households who own the entire capital stock and impatient ones without any physical wealth. More specifically, we prove (i) that there exists a unique steady state equilibrium that is globally asymptotically stable and (ii) that along every equilibrium the most patient household owns the entire capital of the economy after some finite time. Furthermore, we prove that despite the presence of the no-borrowing constraints all equilibria are efficient. Our results are derived for the continuous-time formulation of the model that was originally used by Ramsey, and they stand in stark contrast to results that - over the last three decades - have been found in the discrete-time version of the model.