Synergistic Model of Cardiac Function with a Heart Assist Device

The breakdown of cardiac self-organization leads to heart diseases and failure, the number one cause of death worldwide. The left ventricular pressure–volume relation plays a key role in the diagnosis and treatment of heart diseases. Lumped-parameter models combined with pressure–volume loop analysis are very effective in simulating clinical scenarios with a view to treatment optimization and outcome prediction. Unfortunately, often invoked in this analysis is the traditional, time-varying elastance concept, in which the ratio of the ventricular pressure to its volume is prescribed by a periodic function of time, instead of being calculated consistently according to the change in feedback mechanisms (e.g., the lack or breakdown of self-organization) in heart diseases. Therefore, the application of the time-varying elastance for the analysis of left ventricular assist device (LVAD)–heart interactions has been questioned. We propose a paradigm shift from the time-varying elastance concept to a synergistic model of cardiac function by integrating the mechanical, electric, and chemical activity on microscale sarcomere and macroscale heart levels and investigating the effect of an axial rotary pump on a failing heart. We show that our synergistic model works better than the time-varying elastance model in reproducing LVAD–heart interactions with sufficient accuracy to describe the left ventricular pressure–volume relation

Simulation neuronaler Aktionspotentiale in Hinblick auf Zellform und Physiologie sowie deren Ableitung mittels extrazellulärer Mikroelektroden

Um die Ursache für unterschiedliche Signalformen bei der extrazellulären Ableitung neuronaler Zellsignale zu ermitteln, wird ein detailliertes Neuronenmodell auf Basis der Finiten-Elemente-Methode entwickelt. Im Zuge einer Simulationsstudie werden die Einflüsse von Zellgeometrie und -elektrophysiologie sowie der Zell-Elektroden-Kopplung auf die resultierenden Signalformen analysiert. Die Ergebnisse zeigen, dass der Verlauf des Elektrodensignals signifikant von der Elektrodenposition abhängig ist und sich ein deutlicher Einfluss der Zell-Elektroden-Kopplung auf die Signalamplitude ergibt.In order to investigate the cause for the variety signal shapes present in extracellular measurements of neuronal activity, a detailed neuron model based on the finite element method is created. In a simulation study the impact of geometrical and electrophysiological properties of the neuron as well as several parameters of the neuron-electrode coupling on the derived signal shape is analyzed. Results show a significant dependence of the signal shape on the position of the recording electrode as well as a noticeable influence of the cell-electrode coupling on the signal amplitude

On the membership of invertible diagonal and scalar matrices

AbstractIn this paper, we consider decidability questions that are related to the membership problem in matrix semigroups. In particular, we consider the membership of a given invertible diagonal matrix in a matrix semigroup and then a scalar matrix, which has a separate geometric interpretation. Both problems have been open for any dimensions and are shown to be undecidable in dimension 4 with integral matrices by a reduction of the Post Correspondence Problem (PCP). Although the idea of PCP reduction is standard for such problems, we suggest a new coding technique to cover the case of diagonal matrices

Altered right portal and umbilical vein doppler parameters in fetal macrosomia resulting from pregestational and gestational diabetic mothers: A prospective case-control study

Objective: To evaluate the blood flow of the umbilical vein and right portal vein in macrosomic fetuses of diabetic mothers and investigate the effect of maternal insulin treatment on these blood flows.Material and Methods: This prospective case-control study was con- ducted between March 2019 and December 2019. Fetuses of the 49 pregestational and gestational diabetic mothers who had an abdominal cir- cumference percentile above 97% were evaluated as macrosomic and formed the study group. The study group was divided into two subgroups: patients treated with insulin and those who did not. In the control group, 48 non-diabetic pregnant women with matched gestatio nal weeks whose fetuses are at the 10-90% percentile were included. Time-averaged maximum blood velocity (TAMXV) values of the right portal vein and the free loop of the umbilical vein were measured.Results: The median right portal vein TAMXV value and umbilical vein TAMXV value were found to be significantly higher in diabetic pregnancies (16.25 cm/s, and 15.28 cm/s, respectively) than in the control group (12.76 cm/s, and 13.38 cm/s, respectively, p<0.001). Umbilical and right portal vein flows were similar in macrosomic fetuses of diabetic mothers who were treated with insulin or those who did not. While umbilical vein flow in macrosomic fetuses increased as the gestational age pro gressed (p=0.028), it was observed steadily in normally growing fetuses. Conclusion: The umbilical and right portal vein flows are higher in macro- somic fetuses of diabetic mothers than in appropriately grown fetuses. Maternal insulin treatment does not affect fetal umbilic al vein and right portal vein blood flow in macrosomic fetuses