994-99 Can Late Saphenous Vein Graft Closure Be Predicted by Quantitative Angiographic Analysis Before the Clinical Event?

Angiographic parameters predicting the likelihood of late occlusion of saphenous vein grafts (SVG) have been infrequently described. The Post-CABG Study, a 5-year trial aimed at reducing SVG closure in minimally symptomatic patients 1–11 years Post-CABG, offers a unique view into this event since this study requires an angiogram to document baseline graft patency. In this preliminary study we performed quantitative angiographic analysis (QAA Reiber) comparing the baseline Post-CABG study angiogram to an unscheduled “clinically driven” angiogram. Of 1253 enrolled patients with at least one patent SVG, 35 developed MI or unstable angina associated angiographically with a changed SVG lesion and either total or subtotal occlusion. Average patient age was 58±2 (SEM)years; 97% were male. Years since SVG placement to baseline angiogram averaged 6.5±0.4 (range 2–14). Time from the baseline to the unscheduled angiogram was 22±2 mo (range 3–47). In 28 patients the involved graft was single and in 7 sequential. The SVG insertion segments involved the LCX in 17, RCA in 15 and LAD in 10.ResultsThe initial lesion diameter at the site of the subsequent inciting lesion for all 35 patients averaged 2.58±0.17 mm, or 29.5±3.6% diam. stenosis. (This was defined as the most severe stenosis in any part of the graft in patients with subsequent total graft occlusion, and the exactly matched graft site in those with subtotal occlusion.) In 8 patients the baseline SVG was entirely normal. The initial lesion was >50% stenosis in only 4 patients. At the time of the clinical event, the lesion had progressed to 87±2.6% diam stenosis (N=35). In 16 patients the causal lesion was subtotal, while in 19 the SVG was totally occluded. The mean native vessel — responsible graft anastomotic diameter was 2.33±0.12mm.ConclusionQAA of SVG in asymptomatic patients may not predict subsequent graft closure associated with acute coronary syndromes. The initial site of the lesion is typically of mild-moderate severity, and only later exhibits rapid progression to occlusion

Migration of cations induces reversible performance losses over day/night cycling in perovskite solar cells

Perovskites have been demonstrated in solar cells with a power conversion efficiency of well above 20​%, which makes them one of the strongest contenders for next generation photovoltaics. While there are no concerns about their efficiency, very little is known about their stability under illumination and load. Ionic defects and their migration in the perovskite crystal lattice are some of the most alarming sources of degrdn., which can potentially prevent the commercialization of perovskite solar cells (PSCs)​. In this work, we provide direct evidence of elec. field-​induced ionic defect migration and we isolate their effect on the long-​term performance of state-​of-​the-​art devices. Supported by modeling, we demonstrate that ionic defects, migrating on timescales significantly longer (above 103 s) than what has so far been explored (from 10-​1 to 102 s)​, abate the initial efficiency by 10-​15​% after several hours of operation at the max. power point. Though these losses are not negligible, we prove that the initial efficiency is fully recovered when leaving the device in the dark for a comparable amt. of time. We verified this behavior over several cycles resembling day​/night phases, thus probing the stability of PSCs under native working conditions. This unusual behavior reveals that research and industrial stds. currently in use to assess the performance and the stability of solar cells need to be adjusted for PSCs. Our work paves the way for much needed new testing protocols and figures of merit specifically designed for PSCs

Incorporation of rubidium cations into perovskite solar cells improves photovoltaic performance

All of the cations currently used in perovskite solar cells abide by the tolerance factor for incorporation into the lattice. We show that the small and oxidation-stable rubidium cation (Rb+) can be embedded into a "cation cascade" to create perovskite materials with excellent material properties. We achieved stabilized efficiencies of up to 21.6% (average value, 20.2%) on small areas (and a stabilized 19.0% on a cell 0.5 square centimeters in area) as well as an electroluminescence of 3.8%. The open-circuit voltage of 1.24 volts at a band gap of 1.63 electron volts leads to a loss in potential of 0.39 volts, versus 0.4 volts for commercial silicon cells. Polymer-coated cells maintained 95% of their initial performance at 85 degrees C for 500 hours under full illumination and maximum power point tracking

Incorporation of rubidium cations into perovskite solar cells improves photovoltaic performance

All of the cations currently used in perovskite solar cells abide by the tolerance factor for incorporation into the lattice. We show that the small and oxidation-stable rubidium cation (Rb+) can be embedded into a "cation cascade" to create perovskite materials with excellent material properties. We achieved stabilized efficiencies of up to 21.6% (average value, 20.2%) on small areas (and a stabilized 19.0% on a cell 0.5 square centimeters in area) as well as an electroluminescence of 3.8%. The open-circuit voltage of 1.24 volts at a band gap of 1.63 electron volts leads to a loss in potential of 0.39 volts, versus 0.4 volts for commercial silicon cells. Polymer-coated cells maintained 95% of their initial performance at 85 degrees C for 500 hours under full illumination and maximum power point tracking

Twenty questions about design behavior for sustainability, report of the International Expert Panel on behavioral science for design

How behavioral scientists, engineers, and architects can work together to advance how we all understand and practice design—in order to enhance sustainability in the built environment, and beyond.https://www.nature.com/documents/design_behavior_for_sustainability.pdfPublished versio