Phase Reentrances and Solid Deformations in Confined Colloidal Crystals.

A simple geometric constraint often leads to novel, complex crystalline phases distinct from the bulk. Using thin-film charge colloidal crystals, a model system with tunable interactions, we study the effects of geometric constraints. Through a combination of experiments and simulations, we systematically explore phase reentrances and solid deformation modes concerning geometrical confinement strength, identifying two distinct categories of phase reentrances below a characteristic layer number, N_{c}: one for bcc bulk-stable and another for fcc bulk-stable systems. We further verify that the dominant thermodynamic origin is the nonmonotonic dependence of solids' free energy on the degree of spatial confinement. Moreover, we discover transitions in solid deformation modes between interface-energy and bulk-energy dominance: below a specific layer number, N_{k}, geometric constraints generate unique soft deformation modes adaptive to confinement. These findings on the N-dependent thermodynamic and kinetic behaviors offer fresh insights into understanding and manipulating thin-film crystal structures.

Multiple Scenarios of Low-Temperature Nucleation in Simple Liquids.

Usually, sufficient supercooling of a liquid is employed to bypass the free energy barrier and speed up crystallization. However, lowering the temperature T induces new issues competing with the crystallization, e.g., slow particle motion, geometric frustration, and the glass formation, which complicates our understanding of crystal growth. Here we systematically study the low-temperature nucleation kinetics discriminated by the maximum nucleation rate temperature T_{d} and the glass transition temperature T_{g}. At T_{d}, the ratio of the precursor and geometrically frustrated particles reaches the maximum. When T_{g}

Association between sociodemographic status and cardiovascular risk factors burden in community populations: implication for reducing cardiovascular disease burden.

BACKGROUND: We aimed to evaluate the burden of cardiovascular (CV) risk factors in the community populations of Guangdong Province and its association with sociodemographic status (SDS). METHOD: The data were from the community populations of Guangdong Province who have participated in the China PEACE Million Persons Project between 2016 and 2020 (n = 102,358, women 60.5% and mean age 54.3 years). The prevalence of CV risk factors (smoking, drinking, overweight/obesity, hypertension, dyslipidemia and diabetes mellitus) and its association with SDS (age, sex and socioeconomic status [SES]) was evaluated cross-sectionally. RESULTS: The prevalence of overweight/obesity was 48.9%, hypertension 39.9%, dyslipidemia 18.6%, smoking 17.2%, diabetes mellitus 16.1% and drinking 5.3%. Even in young adults (aged 35-44), nearly 60% had at least 1 CV risk factor. Overweight/obesity often coexisted with other risk factors, including smoking, hypertension, dyslipidemia and diabetes mellitus. The proportion of people with no risk factor decreased with increasing age. Women were more likely than men to have no CV risk factor (29.4% vs. 12.7%). People with ≥ high school degree were more likely than those with < high school to have no risk factor (28.5% vs. 20.4%), and farmers were less likely than non-farmers to have no risk factor (20.8% vs. 23.1%). CONCLUSION: The burden of CV risk factors is high and varied by SDS in the community populations of Guangdong Province. Cost-effective and targeted interventions are needed to reduce the burden of CV risk factors at the population level.

Revealing thermally-activated nucleation pathways of diffusionless solid-to-solid transition.

Solid-to-solid transitions usually occur via athermal nucleation pathways on pre-existing defects due to immense strain energy. However, the extent to which athermal nucleation persists under low strain energy comparable to the interface energy, and whether thermally-activated nucleation is still possible are mostly unknown. To address these questions, the microscopic observation of the transformation dynamics is a prerequisite. Using a charged colloidal system that allows the triggering of an fcc-to-bcc transition while enabling in-situ single-particle-level observation, we experimentally find both athermal and thermally-activated pathways controlled by the softness of the parent crystal. In particular, we reveal three new transition pathways: ingrain homogeneous nucleation driven by spontaneous dislocation generation, heterogeneous nucleation assisted by premelting grain boundaries, and wall-assisted growth. Our findings reveal the physical principles behind the system-dependent pathway selection and shed light on the control of solid-to-solid transitions through the parent phase's softness and defect landscape.

Fast crystal growth at ultra-low temperatures.

It is believed that the slow liquid diffusion and geometric frustration brought by a rapid, deep quench inhibit fast crystallization and promote vitrification. Here we report fast crystal growth in charged colloidal systems under deep supercooling, where liquid diffusion is extremely low. By combining experiments and simulations, we show that this process occurs via wall-induced barrierless ordering consisting of two coupled steps: the step-like advancement of the rough interface that disintegrates frustration, followed by defect repairing inside the newly formed solid phase. The former is a diffusionless collective process, whereas the latter controls crystal quality. We further show that the intrinsic mechanical instability of a disordered glassy state subject to the crystal growth front allows for domino-like fast crystal growth even at ultra-low temperatures. These findings contribute to a deeper understanding of fast crystal growth and may be useful for applications related to vitrification prevention and crystal-quality control.

Revealing roles of competing local structural orderings in crystallization of polymorphic systems.

Most systems have more than two stable crystalline states in the phase diagram, which is known as polymorphism. Crystallization in such a system is often under strong influence of competing orderings linked to those crystals. However, how such competition affects crystal nucleation and ordering toward the final crystalline state is largely unknown. This is primarily because the competition takes place locally and thus is masked by large positional fluctuations. We develop a unique method to correctly identify local symmetries by removing their distortions due to positional fluctuations. This allows us to experimentally access the spatiotemporal fluctuations of local symmetries at a single-particle level in crystallization of a charged colloidal system near the body-centered cubic-face-centered cubic border. Thus, we successfully reveal the crucial roles of competing ordering in the initial selection of polymorphs and the final grain boundary motion toward the most stable state from a microscopic perspective.