RESUMO
The linearity and load insensitivity of the end-systolic pressure-volume-relationship (ESPVR), a parameter that describes the ventricular contractile state, are controversial. We hypothesize that linearity is influenced by a variable overlay of the intrinsic mechanism of autoregulation to afterload (shortening deactivation) and preload (Frank-Starling mechanism). To study the effect of different short-term loading alterations on the shape of the ESPVR, experiments on twenty-four healthy pigs were executed. Preload reductions, afterload increases and preload reductions while the afterload level was increased were performed. The ESPVR was described either by a linear or a bilinear regression through the end-systolic pressure volume (ES-PV) points. Increases in afterload caused a biphasic course of the ES-PV points, which led to a better fit of the bilinear ESPVRs (r2 0.929 linear ESPVR vs. r2 0.96 and 0.943 bilinear ESPVR). ES-PV points of a preload reduction on a normal and augmented afterload level could be well described by a linear regression (r2 0.974 linear ESPVR vs. r2 0.976 and 0.975 bilinear ESPVR). The intercept of the second ESPVR (V0) but not the slope demonstrated a significant linear correlation with the reached afterload level (effective arterial elastance Ea). Thus, the early response to load could be described by the fixed slope of the ESPVR and variable V0, which was determined by the actual afterload. The ESPVR is only apparently nonlinear, as its course over several heartbeats was affected by an overlay of SDA and FSM. These findings could be easily transferred to cardiovascular simulation models to improve their accuracy.
RESUMO
Concerns about sexting are increasingly prevalent in mainstream and academic media despite limited and inconsistent research findings about the practice. Much of this discourse centers around harm and sexting is commonly considered to be a risky behavior. A driving factor in these discussions is the apparent conflation of consensual and nonconsensual acts or sexting behaviors. A systematic review was conducted to determine the extent to which consensual and nonconsensual acts were conflated in the legal, educational, and psychological literatures on sexting, and how nonconsensual sexting was conceptualized within these disciplines. Definitions of sexting varied widely with regard to the inclusion or exclusion of nonconsensual acts. Nonconsensual acts were conceptualized in the following ways: as a risk of sexing, as being the fault of the victim, as bullying, or as a form of violence against women. Implications for research and practice are discussed.