Modeling future cliff-front waves during sea level rise and implications for coastal cliff retreat rates.

It is often assumed that future coastal cliff retreat rates will accelerate as global sea level rises, but few studies have investigated how SLR (sea level rise) might change cliff-front wave dynamics. Using a new simple numerical model, this study simulates the number and type (breaking, broken, or unbroken) of cliff-front waves under future SLR scenarios. Previous research shows breaking waves deliver more energy to cliffs than broken waves, and unbroken waves generate minimal impact. Here, we investigated six cliff-platform profiles from three regions (USA, New Zealand, and UK) with varied tidal ranges and wave climates. Model inputs included 2013-2100 hindcast/forecast incident wave height and tidal water level, and three future SLR scenarios. Results show the number of both cliff-front breaking and broken waves generally increase for a high-elevation (relative to tide) cliff-platform junction. In contrast, breaking/broken wave occurrence decrease by 38-92% for a near-horizontal shore platform with a low-elevation cliff-platform junction under a high SRL scenario, leading to high (96-97%) unbroken wave occurrence. Overall, results suggest the response of cliff-front waves to future SLR is complex and depends on shore platform geometries and SLR scenarios, indicating that future cliff retreat rates may not homogeneously accelerate under SLR.

Reef islands have continually adjusted to environmental change over the past two millennia.

Global environmental change is identified as a driver of physical transformation of coral reef islands over the past half-century, and next 100 years, posing major adaptation challenges to island nations. Here we resolve whether these recent documented changes in islands are unprecedented compared with the pre-industrial era. We utilise radiometric dating, geological, and remote sensing techniques to document the dynamics of a Maldivian reef island at millennial to decadal timescales. Results show the magnitude of island change over the past half-century (±40 m movement) is not unprecedented compared with paleo-dynamic evidence that reveals large-scale changes in island dimension, shape, beach levels, as well as positional changes of ±200 m since island formation ~1,500 years ago. Results highlight the value of a multi-temporal methodological approach to gain a deeper understanding of the dynamic trajectories of reef islands, to support development of adaptation strategies at timeframes relevant to human security.

Quantitative magnetic resonance first-pass perfusion analysis: inter- and intraobserver agreement.

Magnetic resonance first-pass (MRFP) imaging awaits longitudinal clinical trials for quantification of myocardial perfusion. The purpose of this study was to assess inter- and intraobserver agreement of this method. Seventeen MRFP studies (14 rest and 3 under adenosine-induced hyperemia) from 14 patients were acquired. Two observers visually graded study quality. Each study was subdivided into eight regions. Both observers analyzed all 17 studies (8 x 17 = 136 regions) for interobserver agreement. Each observer then analyzed 10 of the 17 studies a second time (2 x 8 x 10 = 160 regions) for intraobserver agreement. Signal intensity curves were obtained with Argus software (Siemens, Iselin, NJ). The maximum amplitude of the impulse response function (Rmax) and the change of signal intensity (deltaSImax) of the contrast bolus were determined. Intraclass correlation coefficient was used to determine intra- and interobserver agreement. The quality was good or excellent in 14 studies. Intraobserver agreement of Rmax and deltaSImax were good (0.85 and 0.80, n = 160). Interobserver agreement of Rmax was fair (0.55, n = 136) but improved after exclusion of poor-quality studies (0.88, n = 112). Interobserver agreement of deltaSImax was good (0.73) and improved less than Rmax with study quality (0.83). Interobserver agreement for Rmax in individual myocardial regions before and after exclusion of studies with poor quality changed most markedly in lateral and posterior regions (0.69 and 0.65 vs. 0.97 and 0.94), where signal-to-noise ratios were reduced compared with anteroseptal regions (p < 0.01). Analysis of MRFP images provides good intraobserver agreement. Interobserver agreement of the quantitative perfusion analysis is good under the premise of good image quality.

Stunned myocardium during extracorporeal membrane oxygenation.

The "stunned myocardium" is a syndrome of reversible myocardial dysfunction that may be mediated by oxygen-derived free radicals. This phenomenon has been seen in some neonates undergoing extracorporeal membrane oxygenation. We performed echocardiograms and measured creatine phosphokinase isoenzymes and lipid peroxide levels in 16 neonates before, during, and after extracorporeal membrane oxygenation. Infants who developed stunned myocardia by echocardiography did so shortly after initiation of bypass and exhibited concurrent elevations of the MB fraction of creatine phosphokinase. Lipid peroxide levels did not simultaneously rise. These data suggest that oxygen-derived free radicals may not cause the stunned myocardium seen in neonates undergoing extracorporeal membrane oxygenation.