Despite advances over the past decade, the incidence of cardiogenic shock secondary to acute myocardial infarction has increased, with an unchanged mortality near 50%. Recent trials have not ...clarified the best strategies in treatment. While dedicated cardiac shock centers are being established, there are no standardized agreements on the utilization of mechanical circulatory support and the timeliness of percutaneous coronary intervention strategies. In some centers and prospective registries, outcomes after placement of advanced mechanical circulatory support prior to reperfusion therapy with percutaneous coronary intervention have been encouraging with improved survival. Here, we suggest systems of care with a treatment pathway for patients with acute myocardial infarction complicated by cardiogenic shock.
Gallium Nitride (GaN) high electron-mobility transistors (HEMTs) can operate at very high power-density levels, which may cause a significant temperature rise in the transistor channel. In addition, ...surface and substrate energy levels, or "traps," can cause strong dispersion effects from pulsed I-V down to dc timescales. Such effects, for both simulation accuracy and device reliability purposes, must be accounted for in any nonlinear device model. In this paper, a novel nonlinear high-power GaN HEMT equivalent circuit electrothermal model is described. Features of the model include a nonlinear thermal subnetwork that is capable of capturing the well-known inherent nonlinear thermal resistance and capacitance of GaN material. Also included is a comprehensive dispersion model that can be extracted and modeled from simple measurements. The model can very accurately predict the pulsed I - V curves at different pulse widths and duty cycles from isothermal up to the safe-operating area limit. Large-signal one-tone, two-tone, and frequency sweep tests show excellent agreement with measurements. Finally, a continuous class-F amplifier is fabricated, and large-signal frequency sweeps are performed. Comparison between the measured and modeled amplifier metrics demonstrate that the model remains accurate over a 50% bandwidth under real-world conditions.
We investigate deviations from the plane wave model in the interaction of charged particles with strong electromagnetic fields. A general result is that integrability of the dynamics is lost when ...going from lightlike to timelike or spacelike field dependence. For a special scenario in the classical regime we show how the radiation spectrum in the spacelike (undulator) case becomes well-approximated by the plane wave model in the high-energy limit, despite the two systems being Lorentz inequivalent. In the quantum problem, there is no analogue of the WKB-exact Volkov solution. Nevertheless, WKB and uniform-WKB approaches give good approximations in all cases considered. Other approaches that reduce the underlying differential equations from second to first order are found to miss the correct physics for situations corresponding to barrier transmission and wide-angle scattering.
Self-determination theory (SDT) posits the importance of three basic psychological needs (i.e., relatedness, autonomy, and competence) in promoting achievement. However, some cross-cultural ...researchers have cast doubt on the generalizability of the theory to non-Western cultures. The primary aim of the study was to test whether provision of support for relatedness, autonomy, and competence would be associated with achievement across both Western and Eastern cultures.
We drew on a subsample of students from the Program for International Student Assessment (PISA) (n = 92,325 students from Australia, Canada, New Zealand, UK, and USA (Western societies); and Hong Kong SAR, Japan, Macau SAR, Shanghai, South Korea, and Taipei (Eastern societies); 46,006 were females and 46,319 were males, with a mean age of 15.77 (SD = 0.29) years). We used multi-group confirmatory factor analysis (MG-CFA) and multi-group structural equation modeling (MG-SEM) to analyze the data.
Provision of the three basic needs correlated positively with achievement across cultures, providing broad support for the cross-cultural universality of SDT. MG-SEM indicated that relatedness and autonomy support were equally important for student achievement in both Western and Eastern cultures, whereas competence support was found to be more important to students in the West than in the East.
Findings support the cross-cultural relevance of SDT while at the same time highlighting important cultural variations such as greater importance of competence support in the West, suggesting the need to be cognizant of both cross-cultural universality and variability in motivational theorizing.
Subantarctic Mode Water (SAMW) in the Pacific forms in two distinct pools in the south central and southeast Pacific, which subduct into the ocean interior and impact global storage of heat and ...carbon. Wintertime thickness of the central and eastern SAMW pools vary predominantly out of phase with each other, by up to ±150 m between years, resulting in an interannual thickness see‐saw. The thickness in the eastern (central) pool is found to be strongly positively (negatively) correlated with both the Southern Annular Mode (SAM) and El Niño–Southern Oscillation (ENSO). The relative phases of the SAM and ENSO set the SAMW thickness, with in phase reinforcing modes in 2005–2008 and 2012–2017 driving strong differences between the pools. Between 2008 and 2012 out of phase atmospheric modes result in less coherent SAMW patterns. SAMW thickness is dominated by local formation driven by SAM and ENSO modulated wind stress and turbulent heat fluxes.
Plain Language Summary
The Southern Ocean around Antarctica is a dominant pathway for moving heat and carbon from the atmosphere into the ocean interior, trapping it for hundreds of years. Most of this uptake is achieved through the formation of “mode waters”, homogeneous layers of water several hundred meters thick, by sinking and overturning as surface waters cool in winter. We find that two distinct pools of mode water in the South Pacific vary dramatically in winter thickness and volume from year to year. They vary in opposition to one another; when one is thicker than normal the other is thinner, with the pattern reversing after a year or so. We show that this “see‐saw” in thickness is strongest when the two main atmospheric patterns of climate variability over the Southern Ocean are reinforcing one another and weaken when they oppose one another. The combination of these patterns of atmospheric variability sets local mode water thickness via surface winds and ocean heat loss. The discovery of such strong dependence of mode water heat content on these atmospheric patterns is important for climate. Atmospheric variability is predicted to change into the future, potentially impacting heat uptake by mode waters and influencing global surface temperatures.
Key Points
South Pacific Subantarctic Mode Water (SAMW) layers display large (±150 m) changes in thickness from year to year
Two distinct pools of South Pacific SAMW exist and their thicknesses see‐saw out of phase with one another
The phase and magnitude of variability are set by changes in wind stress and heat flux driven by the main atmospheric modes of variability
In reptiles, reproductive maturity is often determined by size rather than age. Consequently, growth early in life may influence population dynamics through effects on generation time and survival to ...reproduction. Because reproductive phenology and pre‐ and post‐natal growth are temperature dependent, environmental conditions may induce multi‐species cohort effects on body size in sympatric reptiles. I present evidence of this using 10 years of neonatal size data for three sympatric viviparous snakes, Dekay's Brown snakes (Storeria dekayi), Red‐bellied Snakes (S. occipitomaculata), and Common Garter snakes (Thamnophis sirtalis). End‐of‐season neonatal size varied in parallel across species such that snout–vent length was 36%–61% greater and mass was 65%–223% greater in years when gestating females could achieve higher April–May (vs. June–July or August–September) operative temperatures. Thus, temperature had a larger impact during follicular enlargement and ovulation than during gestation or post‐natal growth. Multi‐species cohort effects like these may affect population dynamics and the magnitude of these effects may increase with climate change.
Sympatric snakes exhibit parallel patterns of neonatal size variation among years. End‐of‐season neonatal size is greater in years when females achieve high operative temperatures for more time in spring during follicle enlargement and ovulation. Multi‐species cohort effects like these may affect population dynamics and increase with climate change.
Research on learning engagement and cognitive load theory have proceeded in parallel with little cross-over of ideas. The aim of this research was to test an integrative model that examines how prior ...knowledge influences learning engagement via cognitive load and help-seeking strategies. A sample of 356 students from two middle schools in the north of China participated in the study. Analyses using structural equation modeling revealed that prior knowledge was positively associated with learning engagement, and that this relationship was mediated by cognitive load and instrumental help-seeking. Cognitive load also mediated the impact of prior knowledge on instrumental help-seeking, executive help-seeking and avoidance of help-seeking. The study shows that students with more prior knowledge and lower cognitive load are able to exercise higher levels of instrumental help-seeking, leading to good quality learning engagement. On the other hand, students with less prior knowledge and higher cognitive load are less able to engage in instrumental help-seeking, leading to lower engagement. Based on the research findings, recommendations for how teachers can improve learning engagement through decreasing cognitive load are discussed.
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