The molecular-level details of crystallization remain unclear for many systems. Previous work has speculated on the phenomenological similarities between molecular crystallization and protein folding. Here we demonstrate that molecular crystallization can involve funnel-shaped potential energy landscapes through a detailed analysis of mixed gas hydrate nucleation, a prototypical multicomponent crystallization process. Through this, we contribute both: (i) a powerful conceptual framework for exploring and rationalizing molecular crystallization, and (ii) an explanation of phenomenological similarities between protein folding and crystallization. Such funnel-shaped potential energy landscapes may be typical of broad classes of molecular ordering processes, and can provide a new perspective for both studying and understanding these processes. nucleation | gas clathrate hydrates | potential energy landscapes | crystallization funnel | molecular dynamics simulation M olecular crystallization and its inhibition are important to a broad range of fields. For example, some organisms [such as Antarctic fish (1) and winter rye (2)] have developed a rich chemistry of antifreeze proteins to control internal freezing, and there is significant interest in exploiting antifreeze proteins for food applications (e.g., see ref.3). Gas hydrate formation in oil and gas pipelines is a major industrial concern (4). For pharmaceuticals, there is much interest in understanding and controlling crystal polymorphism (e.g., see ref. 5). A better understanding of molecular crystallization, and factors influencing these processes, has potential to aid further advancements in such fields. As highlighted by a recent review on crystallization (6), traditional theoretical models of crystallization (e.g., classical nucleation theory) have proven to be problematic for a variety of systems and there remain technical challenges to studying crystallization both experimentally and computationally, so a clear understanding of crystal nucleation has yet to emerge.Molecular crystallization is one of the major classes of molecular ordering processes. Other molecular ordering processes include micelle formation, the formation of coordination polymers, and protein folding. Previous work has asserted, although not substantiated, that crystallization and protein folding are somehow similar processes. For example, protein folding has been speculatively described as a first-order phase transition similar to liquidsolid transitions (7). It has also been proposed that both the waterice transition and protein folding are difficult to study in silico because both are complex searches for relatively few ordered structures among numerous disordered alternative structures (8). The aim of this study is twofold: (i) to provide a conceptual description of molecular crystallization (simply referred to as crystallization henceforth), and (ii) to provide an explanation of the apparent similarities between crystallization and protein folding. On the basis of extensive simulati...

While previous work exists on how to conduct and disseminate insights from problem-driven visualization projects and design studies, the literature does not address how to accomplish these goals in transdisciplinary teams in ways that advance all disciplines involved. In this paper we introduce and define a new methodological paradigm we call design by immersion, which provides an alternative perspective on problem-driven visualization work. Design by immersion embeds transdisciplinary experiences at the center of the visualization process by having visualization researchers participate in the work of the target domain (or domain experts participate in visualization research). Based on our own combined experiences of working on cross-disciplinary, problemdriven visualization projects, we present six case studies that expose the opportunities that design by immersion enables, including (1) exploring new domain-inspired visualization design spaces, (2) enriching domain understanding through personal experiences, and (3) building strong transdisciplinary relationships. Furthermore, we illustrate how the process of design by immersion opens up a diverse set of design activities that can be combined in different ways depending on the type of collaboration, project, and goals. Finally, we discuss the challenges and potential pitfalls of design by immersion.

The Shinoda-DeVane-Klein (SDK) model is herein demonstrated to be a viable coarse-grain model for performing molecular simulations of polyethylene (PE), affording new opportunities to advance molecular-level, scientific understanding of PE materials and processes. Both structural and dynamical properties of entangled PE melts are captured by the SDK model, which also recovers important aspects of PE crystallization phenomenology. Importantly, the SDK model can be used to represent a variety of materials beyond PE and has a simple functional form, making it unique among coarse-grain PE models. This study expands the suite of tools for studying PE in silico and paves the way for future work probing PE and PE-based composites at the molecular level.

We demonstrate that nascent polymer crystals (i.e., nuclei) are anisotropic entities, with neither spherical nor cylindrical geometry, in contrast to previous assumptions. In fact, cylindrical, spherical, and other high symmetry geometries are thermodynamically unfavorable. Moreover, post-critical transitions are necessary to achieve the lamellae that ultimately arise during the crystallization of semicrystalline polymers. We also highlight how inaccurate treatments of polymer nucleation can lead to substantial errors (e.g., orders of magnitude discrepancies in predicted nucleation rates). These insights are based on quantitative analysis of over four million crystal clusters from the crystallization of prototypical entangled polyethylene melts. New comprehensive bottom-up models are needed to capture polymer nucleation.