In Situ Transmission Electron Microscopy Investigation of Melting/Evaporation Kinetics in Anisotropic Gold Nanoparticles

We report on thermal stability and phase transition behaviors of triangular Au nanoprisms through in situ heating transmission electron microscopy. With rising temperature, Au nanoprisms exhibit fluctuating surface reconstructions at the corner regions. When a quasi-melting state is reached at the temperature below bulk melting points, the evaporation is initiated commonly at a corner with low curvature and containing sharp intersection points. The subsequent annealing process leads to the gradual evaporation, which, in the absence of thick carbon coverages, is accompanied by marked shape reconstructions. The thermal stability and evaporation behaviors are not evidently regulated by nanoprism aggregations.

Be water my friend: mesh assimilation

Inspired by the ability of water to assimilate any shape, if being poured into it, regardless if flat, round, sharp, or pointy, we present a novel, high-quality meshing method. Our algorithm creates a triangulated mesh, which automatically refines where necessary and accurately aligns to any target, given as mesh, point cloud, or volumetric function. Our core optimization iterates over steps for mesh uniformity, point cloud projection, and mesh topology corrections, always guaranteeing mesh integrity and $$\epsilon $$ ϵ -close surface reconstructions. In contrast with similar approaches, our simple algorithm operates on an individual vertex basis. This allows for automated and seamless transitions between the optimization phases for rough shape approximation and fine detail reconstruction. Therefore, our proposed algorithm equals established techniques in terms of accuracy and robustness but supersedes them in terms of simplicity and better feature reconstruction, all controlled by a single parameter, the intended edge length. Due to the overall increased versatility of input scenarios and robustness of the assimilation, our technique furthermore generalizes multiple established approaches such as ballooning or shrink wrapping.

Post-LGM evolution of the Dora Baltea glacial system and paleoclimatic implications in the Western Italian Alps

<p>Alpine glaciers repeatedly advanced and retreated from the high Alps to the forelands during the Quaternary and most recently reached their maximum extent and thickness during the Last Glacial Maximum (LGM, 26.5-19.0 ka ago)<sup> [1]</sup>. After the LGM, glaciers abandoned the Alpine foreland and retreated within the internal valleys. However, post-LGM withdrawal was not continuous but interrupted by stages of ice stasis or re-advance (stadials<sup> [2]</sup>), related to episodes of temporary climatic cooling. Glacial landforms and deposits associated to post-LGM ice stadials have been recognised across the Alps <sup>[2]</sup>. Our study contributes to this line of research by quantitatively reconstructing the age and configuration of several ice stages from the LGM to the Holocene, within the Dora Baltea (DB) catchment (SW Alps, Italy).</p><p>Following a detailed geomorphological mapping of glacial landforms and deposits, sixteen erratic boulders and two glacially-polished bedrocks were sampled along the DB valley for <em>in-situ</em><sup><em> </em>10</sup>Be surface-exposure dating, and five samples for luminescence dating were collected from fluvio-lacustrine and fluvio-glacial deposits. The obtained chronologies, combined with recalculated <sup>10</sup>Be surface-exposure ages from previous works in the study area <sup>[1, 3, 4, 5]</sup>, constrain seven post-LGM ice stages in the DB valley. The first three retreat stages occurred between the end of the LGM and the early Lateglacial, probably with rapid ice decay. The following three stages correspond to the well-known Gschnitz, Daun and Egesen Alpine Lateglacial stadials <sup>[2]</sup>, while we also identified a late-Holocene ice re-advance in the upstream DB catchment.</p><p>Paleo-ice configurations of each stage (including the LGM) were obtained with a semi-automatic ArcGIS routine (similar approach to GlaRe ArcGIS toolbox <sup>[6]</sup>), based on the areal interpolation of 2D ice surface profiles generated through Profiler v.2 <sup>[7]</sup>. Glacier equilibrium-line altitudes (ELAs) were computed for the eight 3D ice surface reconstructions <sup>[8]</sup>, with the aim of deriving potential paleoclimatic implications of the different reconstructed ice stages in comparison to other paleoclimatic proxies.</p><p> </p><p><strong>References</strong></p><p><sup>[1] </sup>Wirsig, C. et al., 2016, Quaternary Science Reviews.</p><p><sup>[2] </sup>Ivy-ochs, S., 2015, Cuadernos de Investigación Geográfica.</p><p><sup>[3] </sup>Gianotti, F. et al., 2015, Alpine and Mediterranean Quaternary.</p><p><sup>[4] </sup>Deline, P. et al., 2015, Quaternary Science Reviews.</p><p><sup>[5] </sup>Le Roy, M., 2012. Université Grenoble Alpes.</p><p><sup>[6] </sup>Pellitero, R. et al., 2016, Computers and Geosciences.</p><p><sup>[7] </sup>Benn, D., Hulton, N., 2010, Quaternary Science Reviews.</p><p><sup>[8] </sup>Pellitero, R. et al., 2015, Computers and Geosciences.</p>