Due to the abundance of ice on earth, the phase transition of ice plays crucially important roles in various phenomena in nature. Hence, the molecular-level understanding of ice crystal surfaces holds the key to unlocking the secrets of a number of fields. In this study we demonstrate, by laser confocal microscopy combined with differential interference contrast microscopy, that elementary steps (the growing ends of ubiquitous molecular layers with the minimum height) of ice crystals and their dynamic behavior can be visualized directly at air-ice interfaces. We observed the appearance and lateral growth of two-dimensional islands on ice crystal surfaces. When the steps of neighboring two-dimensional islands coalesced, the contrast of the steps always disappeared completely. We were able to discount the occurrence of steps too small to detect directly because we never observed the associated phenomena that would indicate their presence. In addition, classical two-dimensional nucleation theory does not support the appearance of multilayered two-dimensional islands. Hence, we concluded that two-dimensional islands with elementary height (0.37 and 0.39 nm on basal and prism faces, respectively) were visualized by our optical microscopy. On basal and prism faces, we also observed the spiral growth steps generated by screw dislocations. The distance between adjacent spiral steps on a prism face was about 1∕20 of that on a basal face. Hence, the step ledge energy of a prism face was 1∕20 of that on a basal face, in accord with the known lowertemperature roughening transition of the prism face.in situ observation | monomolecular steps | two-dimensional nucleation growth | spiral growth I ce is one of the most abundant materials on earth, and its phase transition governs a wide variety of phenomena, such as weather, environment-related issues, life in a cryosphere, and cosmic evolution, etc. Hence the molecular-level understanding of ice crystal surfaces is crucially important. For example, ice crystal surfaces play a key role in heterogeneous physical/chemical reactions, such as the degradation of ozone and organic compounds adsorbed on ice crystal surfaces by UV light irradiation (1-4), the suppression of the growth of ice in living things by antifreeze proteins adsorbed on ice crystal surfaces (5-8), etc., as well as in the growth and sublimation/melting of ice crystals.A crystal bounded by flat crystal faces grows layer by layer (9, 10), utilizing laterally growing molecular layers that have the minimum height determined by the crystal structure. Hence, growing ends of such molecular layers, so-called "elementary steps," which ubiquitously exist on a crystal surface, play a key role during the physical/chemical reactions and the growth and sublimation/melting of ice crystals. Therefore to clarify such phenomena at the molecular level, first one has to observe elementary steps on ice crystal surfaces.Many optical microscopy studies have been carried out to date to observe the surface morphology of ice crystals, such ...

Antifreeze glycoproteins (AFGPs) are a necessary tool for the survival of fish that live in subfreezing environments [Yeh, Y.; Feeney, R. E. Antifreeze proteinssStructures and mechanisms of function. Chem. ReV. 1996, 96 (2), 601-617]. Although scientists agree that these proteins arrest ice crystal growth by a surface adsorption mechanism, the exact nature of the interaction remains an open question. Here, we study the adsorption kinetics of AFGPs during solution ice crystal growth using confocal fluorescence microscopy within and just below the freezing-melting temperature hysteresis region. The AFGP kinetics at the ice surface reveal a two-step inhibition process: (i) incomplete adsorption or a weak interaction that modifies the surface for (ii) a stronger interaction to achieve the complete adsorption necessary to halt growth. The growth is modified from a rough interface to a faceted one, and growth is halted at supercoolings less than 0.05°C. However, growth resumes, and the proteins desorb, return to the solution phase, and are not incorporated into the ice crystal as previously proposed. Our findings are contrary to an AFGP mechanism described by the Gibbs-Thomson model. We argue that an alternative explanation must include a solvated protein interacting with a solvated ice surface. While thermodynamics considerably alter the interfacial region, antifreeze action is a purely kinetic phenomenon.

We propose a model of pattern formation in the growth of snow crystals that takes into account the actual elemental processes relevant to the growth of crystals, i.e. , a surface kinetic process for incorporating molecules into a crystal lattice and a diffusion process. This model gives a clear correspondence between the patterns produced and the actual growth conditions such as supersaturation and the diffusion coefficient. Circular patterns due to kinetic roughening, hexagonal patterns, and dendritic patterns are obtained starting from a circular crystal under various growth conditions. We analyze these patterns and discuss the mechanisms of appearance of round patterns, the development of hexagonal patterns, and the formation of dendritic patterns of snow crystals. Finally, it is shown that the dimensionless crystal size with reference to the mean free path of a water molecule plays an important role in the pattern formation of growing snow crystals.

We investigate a simple experimental system using candles; stable combustion is seen when a single candle burns, while oscillatory combustion is seen when three candles burn together. If we consider a set of three candles as a component oscillator, two oscillators, that is, two sets of three candles, can couple with each other, resulting in both in-phase and antiphase synchronization depending on the distance between the two sets. The mathematical model indicates that the oscillatory combustion in a set of three candles is induced by a lack of oxygen around the burning point. Furthermore, we suggest that thermal radiation may be an essential factor of the synchronization.