Hemodynamic and electromechanical effects of paraquat in rat heart

Paraquat (PQ) is a highly lethal herbicide. Ingestion of large quantities of PQ usually results in cardiovascular collapse and eventual mortality. Recent pieces of evidence indicate possible involvement of oxidative stress- and inflammation-related factors in PQ-induced cardiac toxicity. However, little information exists on the relationship between hemodynamic and cardiac electromechanical effects involved in acute PQ poisoning. The present study investigated the effects of acute PQ exposure on hemodynamics and electrocardiogram (ECG) in vivo, left ventricular (LV) pressure in isolated hearts, as well as contractile and intracellular Ca2+ properties and ionic currents in ventricular myocytes in a rat model. In anesthetized rats, intravenous PQ administration (100 or 180 mg/kg) induced dose-dependent decreases in heart rate, blood pressure, and cardiac contractility (LV +dP/dtmax). Furthermore, PQ administration prolonged the PR, QRS, QT, and rate-corrected QT (QTc) intervals. In Langendorff-perfused isolated hearts, PQ (33 or 60 μM) decreased LV pressure and contractility (LV +dP/dtmax). PQ (10–60 μM) reduced the amplitudes of Ca2+ transients and fractional cell shortening in a concentration-dependent manner in isolated ventricular myocytes. Moreover, whole-cell patch-clamp experiments demonstrated that PQ decreased the current amplitude and availability of the transient outward K+ channel (Ito) and altered its gating kinetics. These results suggest that PQ-induced cardiotoxicity results mainly from diminished Ca2+ transients and inhibited K+ channels in cardiomyocytes, which lead to LV contractile force suppression and QTc interval prolongation. These findings should provide novel cues to understand PQ-induced cardiac suppression and electrical disturbances and may aid in the development of new treatment modalities.

Origins of Negative and Positive Electromechanical Response of Oligopeptide Piezoelectrics

In response to an applied electric field, materials and even individual molecules can exhibit electromechanical response. Previous work has demonstrated the piezoelectric distortion of polar organic crystals, biomaterials, and even single molecular monolayers, increasing length in response to the change in potential energy of interaction between the polarization or dipole moment and the applied electric field. In this work, we demonstrate through density functional calculations that helical oligopeptides, depending on sequence can exhibit both positive and surprisingly also negative piezoresponse. While the overall molecular dipole moment may favor positive piezoresponse, individual hydrogen bonding interactions along the backbone have the opposite direction, enabling tailored sequences to yield either net expansion or contraction in response to an electric field. While negative piezoresponse has largely been considered in polyvinylidene difluoride (PVDF) and related systems, understanding the atomic and molecular basis for both electromechanical effects will yield interesting new applications.

Origins of Negative and Positive Electromechanical Response of Oligopeptide Piezoelectrics

In response to an applied electric field, materials and even individual molecules can exhibit electromechanical response. Previous work has demonstrated the piezoelectric distortion of polar organic crystals, biomaterials, and even single molecular monolayers, increasing length in response to the change in potential energy of interaction between the polarization or dipole moment and the applied electric field. In this work, we demonstrate through density functional calculations that helical oligopeptides, depending on sequence can exhibit both positive and surprisingly also negative piezoresponse. While the overall molecular dipole moment may favor positive piezoresponse, individual hydrogen bonding interactions along the backbone have the opposite direction, enabling tailored sequences to yield either net expansion or contraction in response to an electric field. While negative piezoresponse has largely been considered in polyvinylidene difluoride (PVDF) and related systems, understanding the atomic and molecular basis for both electromechanical effects will yield interesting new applications.

Ripples in Graphene Sheets and Nanoribbons

We study the influence of ripple waves on graphene sheets and graphene nanoribbons. Such waves are originating from the electromechanical effects, among other possible mechanisms. By considering variations in the in-plane and out-of-plane displacement vector, we show that the spontaneous generation of ripple waves has no preferred orientation. Intrinsic properties of ripple waves induce a large pseudopotential that in its turn is to induce large pseudomagentic fields that can be implemented into the band engineering of graphene structures.

Multiphysical computation of the structural bending in a bottom-drive VCM

Purpose This paper intends to lay a background knowledge towards the feasibility of developing a bottom-drive variable capacitance micromotor (VCM) using a surface micromachining process (SMP). The purpose of this paper is to determine the possibility of neglecting the bending of the rotor plates caused by the electrostatic normal forces when deploying a set of mechanical supports. Design/methodology/approach A multiphysics simulation approach is considered in order to analyse the coupled electromechanical effects in a steady state and to evaluate if the proposed geometries are useful to reduce the bending of the plates. Findings A surfaced micromachined bottom-drive VCM requires mechanical reinforcement in order to eliminate the risk of an electrical short circuit caused by the deformation in the rotor plates. The combination of an external supporting ring and anchored structural ribs on top of the rotor poles is sufficient to neglect the deformation in the poles of the rotor. Originality/value An original analysis with the objective of setting a background in the development of a bottom-drive electrostatic micromotor using a SMP is presented.