at which nucleation occurs is determined largely by the size of the nanodroplets present (10). Could the precritical clusters observed by Gebauer et al. also be the result of stabilization of calcium carbonate clusters by another species present as an impurity? This mechanism would provide a basis for stabilizing precritical clusters in a free-energy minimum and does not contradict classical nu...

Nucleation and growth of Ti3Al ?2 ordered domains in ?-Ti–Al–X alloys were characterised using a combination transmission electron microscopy, atom probe tomography small angle X-ray scattering. Model based on Ti–7Al (wt.%) containing O, V Mo aged at 550?C for times up to 120d the resulting precipitate dispersions observed intermediate points. Precipitates grew around 30nm size, with volume fra...

Due to their net warming effect, cirrus clouds play a crucial role in the climate system. A recently proposed climate engineering mechanism (CEM) intends to reduce high cloud cover by seeding cirrus clouds with efficient ice nuclei (IN) and therefore cool climate. Here, the susceptibility of cirrus clouds to the injection of ice nuclei in the upper troposphere is investigated in the extended Co...

Hydroxyapatite (HAP) participates in vertebral bone and tooth formation by a nonclassical hitherto unknown nucleation mechanism, in which amorphous precursors form and transform during long induction periods. Elucidation of the mechanism by which amorphous precursors assemble and transform is essential to understanding how hard tissues form in vivo and will advance the design and fabrication of...

Experimental study of the atomic mechanism in melting and freezing processes remains a formidable challenge. We report herein on a unique material system that allows for in situ growth of bismuth nanoparticles from the precursor compound SrBi2Ta2O9 under an electron beam within a high-resolution transmission electron microscope (HRTEM). Simultaneously, the melting and freezing processes within ...

Acoustically sensitive emulsion droplets composed of a liquid perfluorocarbon have the potential to be a highly efficient system for local drug delivery, embolotherapy, or for tumor imaging. The physical mechanisms underlying the acoustic activation of these phase-change emulsions into a bubbly dispersion, termed acoustic droplet vaporization, have not been well understood. The droplets have a ...

Cirrus clouds are ubiquitous in the tropical tropopause region and play a major role in the Earth's climate. Any changes to cirrus abundance due to natural or anthropogenic influences must be considered to evaluate future climate change. The detailed impact of cirrus clouds on climate depends on ice particle number, size, morphology, and composition. These properties depend in turn on the nucle...