Tunable liquid-solid hybrid thermal metamaterials with a topology transition.

Thermal metamaterials provide rich control of heat transport which is becoming the foundation of cutting-edge applications ranging from chip cooling to biomedical. However, due to the fundamental laws of physics, the manipulation of heat is much more constrained in conventional thermal metamaterials where effective heat conduction with Onsager reciprocity dominates. Here, through the inclusion of thermal convection and breaking the Onsager reciprocity, we unveil a regime in thermal metamaterials and transformation thermotics that goes beyond effective heat conduction. By designing a liquid-solid hybrid thermal metamaterial, we demonstrate a continuous switch from thermal cloaking to thermal concentration in one device with external tuning. Underlying such a switch is a topology transition in the virtual space of the thermotic transformation which is achieved by tuning the liquid flow via external control. These findings illustrate the extraordinary heat transport in complex multicomponent thermal metamaterials and pave the way toward an unprecedented regime of heat manipulation.

Giant, magnet-free, and room-temperature Hall-like heat transfer.

Thermal chirality, generically referring to the handedness of heat flux, provides a significant possibility for modern heat control. It may be realized with the thermal Hall effect yet at the high cost of strong magnetic fields and extremely low temperatures. Here, we reveal magnet-free and room-temperature Hall-like heat transfer in an active thermal lattice composed of a stationary solid matrix and rotating solid particles. Rotation breaks the Onsager reciprocity relation and generates giant thermal chirality about two orders of magnitude larger than ever reported at the optimal rotation velocity. We further achieve anisotropic thermal chirality by breaking the rotation invariance of the active lattice, bringing effective thermal conductivity to a region unreachable by the thermal Hall effect. These results could enlighten topological and non-Hermitian heat transfer and efficient heat utilization in ways distinct from phonons.

Higher-Order Topological In-Bulk Corner State in Pure Diffusion Systems.

Compared with conventional topological insulator that carries topological state at its boundaries, the higher-order topological insulator exhibits lower-dimensional gapless boundary states at its corners and hinges. Leveraging the form similarity between Schrödinger equation and diffusion equation, research on higher-order topological insulators has been extended from condensed matter physics to thermal diffusion. Unfortunately, all the corner states of thermal higher-order topological insulator reside within the band gap. Another kind of corner state, which is embedded in the bulk states, has not been realized in pure diffusion systems so far. Here, we construct higher-dimensional Su-Schrieffer-Heeger models based on sphere-rod structure to elucidate these corner states, which we term "in-bulk corner states." Because of the anti-Hermitian properties of diffusive Hamiltonian, we investigate the thermal behavior of these corner states through theoretical calculation, simulation, and experiment. Furthermore, we study the different thermal behaviors of in-bulk corner state and in-gap corner state. Our results would open a different gate for diffusive topological states and provide a distinct application for efficient heat dissipation.

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.

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.

Diffusive Fizeau Drag in Spatiotemporal Thermal Metamaterials.

Fizeau drag means that the speed of light can be regulated by the flow of water, owing to the momentum interaction between photons and moving media. However, the dragging of heat is intrinsically elusive, due to the absence of momentum in thermal diffusion. Here, we design a spatiotemporal thermal metamaterial based on heat transfer in porous media to demonstrate the diffusive analog to Fizeau drag. The space-related inhomogeneity and time-related advection enable the diffusive Fizeau drag effect. Thanks to the spatiotemporal coupling, different propagating speeds of temperature fields can be observed in two opposite directions, thus facilitating nonreciprocal thermal profiles. The phenomenon of diffusive Fizeau drag stands robustly even when the direction of advection is perpendicular to the propagation of temperature fields. These results could pave an unexpected way toward realizing the nonreciprocal and directional transport of mass and energy.

Thermal Willis Coupling in Spatiotemporal Diffusive Metamaterials.

Willis coupling generically stems from bianisotropy or chirality in wave systems. Nevertheless, those schemes are naturally unavailable in diffusion systems described by a single constitutive relation governed by the Fourier law. Here, we report spatiotemporal diffusive metamaterials by modulating thermal conductivity and mass density in heat transfer. The Fourier law should be modified after homogenizing spatiotemporal parameters, featuring thermal Willis coupling between heat flux and temperature change rate. Thermal Willis coupling drives asymmetric heat diffusion, and the diffusion direction is reversible at a critical point determined by the degree of spatiotemporal modulation. Moreover, thermal Willis coupling stands robustly even when only thermal conductivity is modulated. These results may have potential applications for directional diffusion and offer insights into asymmetric manipulation of nonequilibrium mass and energy transfer.

Declining Oxygen Level as an Emerging Concern to Global Cities.

Rising CO2 concentration and temperatures in urban areas are now well-known, but the potential of an emerging oxygen crisis in the world's large cities has so far attracted little attention from the science community. Here, we investigated the oxygen balance and its related risks in 391 global large cities (with a population of more than 1 million people) using the oxygen index (OI), which is the ratio of oxygen consumption to oxygen production. Our results show that the global urban areas, occupying only 3.8% of the global land surface, accounted for 39% (14.3 ± 1.5 Gt/yr) of the global terrestrial oxygen consumption during 2001-2015. We estimated that 75% of cities with a population more than 5 million had an OI of greater than 100. Also, cities with larger OI values were correlated with more frequent heatwaves and severe water withdrawals. In addition, cities with excessively large OI values would likely experience severe hypoxia in extremely calm weather. Thus, mitigation measures should be adopted to reduce the urban OI in order to build healthier and more sustainable cities.

Temperature Trapping: Energy-Free Maintenance of Constant Temperatures as Ambient Temperature Gradients Change.

It is crucial to maintain constant temperatures in an energy-efficient way. Here we establish a temperature-trapping theory for asymmetric phase-transition materials with thermally responsive thermal conductivities. Then we theoretically introduce and experimentally demonstrate a concept of an energy-free thermostat within ambient temperature gradients. The thermostat is capable of self-maintaining a desired constant temperature without the need of consuming energy even though the environmental temperature gradient varies in a large range. As a model application of the concept, we design and show a different type of thermal cloak that has a constant temperature inside its central region in spite of the changing ambient temperature gradient, which is in sharp contrast to all the existing thermal cloaks. This work has relevance to energy-saving heat preservation, and it provides guidance both for manipulating heat flow without energy consumption and for designing new metamaterials with temperature-responsive or field-responsive parameters in many disciplines such as thermotics, optics, electromagnetics, acoustics, mechanics, electrics, and magnetism.

Temperature-Dependent Transformation Thermotics: From Switchable Thermal Cloaks to Macroscopic Thermal Diodes.

The macroscopic control of ubiquitous heat flow remains poorly explored due to the lack of a fundamental theoretical method. Here, by establishing temperature-dependent transformation thermotics for treating materials whose conductivity depends on temperature, we show analytical and simulation evidence for switchable thermal cloaking and a macroscopic thermal diode based on the cloaking. The latter allows heat flow in one direction but prohibits the flow in the opposite direction, which is also confirmed by our experiments. Our results suggest that the temperature-dependent transformation thermotics could be a fundamental theoretical method for achieving macroscopic heat rectification, and it could provide guidance both for the macroscopic control of heat flow and for the design of the counterparts of switchable thermal cloaks or macroscopic thermal diodes in other fields like seismology, acoustics, electromagnetics, and matter waves.

Thermal conduction force under standing and quasistanding temperature field.

Thermal conduction force plays a crucial role in manipulating the local thermal conductivity of crystals. However, due to the diffusive nature of thermal conduction, investigating the force effect is challenging. Recently, researchers have explored the force effect based on the wavelike behavior of thermal conduction, specifically second sound. However, their focus has been primarily on the progressive case, neglecting the more complex standing temperature field case. Additionally, establishing a connection between the results obtained from the progressive case and the standing case poses a challenging problem. In this study, we investigate the force effect of standing and quasistanding temperature fields, revealing distinct characteristics of thermal conduction force. Moreover, we establish a link between the progressive and standing cases through the quasistanding case. Our findings pave the way for research in more intricate scenarios and provide an additional degree of freedom for manipulating the local thermal conductivity of dielectric crystals.

Update on diabetic retinopathy during pregnancy.

Diabetes mellitus (DM) leads to several vascular and neurological complications, including diabetic retinopathy (DR). As the population ages, health problems in certain groups, including children and pregnant women, are drawing more and more attention. Pregnancy is one of the independent risk factors for the development and progression of DR. Pregnancy-induced changes may contribute to or worsen DR, which can cause a tremendous burden on public health. It is essential for pregnant women with DR and their offspring to minimize the risk of vision loss from DR in this population and adverse outcomes by understanding the development and processes behind this process. Thus, we have updated the recent situation of epidemiology, evolution characteristics, risk factors, pathophysiology, pregnancy outcomes for a better understanding of the latest status of DR, helping to improve maternal and neonatal pregnancy outcomes, and promoting health for women with DR.

Deep Learning-Assisted Active Metamaterials with Heat-Enhanced Thermal Transport.

Heat management is crucial for state-of-the-art applications such as passive radiative cooling, thermally adjustable wearables, and camouflage systems. Their adaptive versions, to cater to varied requirements, lean on the potential of adaptive metamaterials. Existing efforts, however, feature with highly anisotropic parameters, narrow working-temperature ranges, and the need for manual intervention, which remain long-term and tricky obstacles for the most advanced self-adaptive metamaterials. To surmount these barriers, heat-enhanced thermal diffusion metamaterials powered by deep learning is introduced. Such active metamaterials can automatically sense ambient temperatures and swiftly, as well as continuously, adjust their thermal functions with a high degree of tunability. They maintain robust thermal performance even when external thermal fields change direction, and both simulations and experiments demonstrate exceptional results. Furthermore, two metadevices with on-demand adaptability, performing distinctive features with isotropic materials, wide working temperatures, and spontaneous response are designed. This work offers a framework for the design of intelligent thermal diffusion metamaterials and can be expanded to other diffusion fields, adapting to increasingly complex and dynamic environments.

Free-form and multi-physical metamaterials with forward conformality-assisted tracing.

Transformation theory, active control and inverse design have been mainstream in creating free-form metamaterials. However, existing frameworks cannot simultaneously satisfy the requirements of isotropic, passive and forward design. Here we propose a forward conformality-assisted tracing method to address the geometric and single-physical-field constraints of conformal transformation. Using a conformal mesh composed of orthogonal streamlines and isotherms (or isothermal surfaces), this method quasi-analytically produces free-form metamaterials using only isotropic media. The geometric nature of this approach allows for universal regulation of both dissipative thermal fields and non-dissipative electromagnetic fields. We experimentally demonstrate free-form thermal cloaking in both two and three dimensions. Additionally, the multi-physical functionalities of our method, including optical cloaking, bending and thermo-electric transparency, confirm its broad applicability. Our method features improvements in efficiency, accuracy and adaptability over previous approaches. This study provides an effective method for designing complex metamaterials with arbitrary shapes across various physical domains.

Parkin depletion delays motor decline dose-dependently without overtly affecting neuropathology in α-synuclein transgenic mice.

BACKGROUND: Mutations of the gene encoding the major component of Lewy bodies (LB), α-synuclein (α-syn), cause autosomal dominant forms of Parkinson's disease (PD), whereas loss-of-function mutations of the gene encoding the multifunctional E3 ubiquitin-protein ligase Parkin account for autosomal recessive forms of the disease. Parkin overproduction protects against α-syn-dependent neurodegeneration in various in vitro and in vivo models, but it remains unclear whether this process is affected by Parkin deficiency. We addressed this issue, by carrying out more detailed analyses of transgenic mice overproducing the A30P variant of human α-syn (hA30Pα-syn) and with two, one or no parkin knockout alleles. RESULTS: Longitudinal behavioral follow-up of these mice indicated that Parkin depletion delayed disease-predictive sensorimotor impairment due to α-syn accumulation, in a dose-dependent fashion. At the end stage of the disease, neuronal deposits containing fibrillar α-syn species phosphorylated at S129 (PS129α-syn) were the predominant neuropathological feature in hA30Pα-syn mice, regardless of their parkin expression. Some of these deposits colocalized with the LB markers ubiquitin and α-syn truncated at D135 (α-synD135), indicating that PS129α-syn is subjected to secondary posttranslational modification (PTM); these features were not significantly affected by parkin dysfunction. CONCLUSIONS: These findings suggest that Parkin deficiency acts as a protective modifier in α-syn-dependent neurodegeneration, without overtly affecting the composition and characteristics of α-syn deposits in end-stage disease.

Coalescence of Pickering emulsion droplets induced by an electric field.

Combining high-speed photography with electric current measurement, we investigate the electrocoalescence of Pickering emulsion droplets. Under a high enough electric field, the originally stable droplets coalesce via two distinct approaches: normal coalescence and abnormal coalescence. In the normal coalescence, a liquid bridge grows continuously and merges two droplets together, similar to the classical picture. In the abnormal coalescence, however, the bridge fails to grow indefinitely; instead, it breaks up spontaneously due to the geometric constraint from particle shells. Such connecting-then-breaking cycles repeat multiple times, until a stable connection is established. In depth analysis indicates that the defect size in particle shells determines the exact merging behaviors: when the defect size is larger than a critical size around the particle diameter, normal coalescence will show up, while abnormal coalescence will appear for coatings with smaller defects.

Adaptive multi-temperature control for transport and storage containers enabled by phase-change materials.

The transportation of essential items, such as food and vaccines, often requires adaptive multi-temperature control to maintain high safety and efficiency. While existing methods utilizing phase change materials have shown promise, challenges related to heat transfer and materials' physicochemical properties remain. In this study, we present an adaptive multi-temperature control system using liquid-solid phase transitions to achieve highly effective thermal management using a pair of heat and cold sources. By leveraging the properties of stearic acid and distilled water, we fabricated a multi-temperature maintenance container and demonstrated temperature variations of only 0.14-2.05% over a two-hour period, underscoring the efficacy of our approach. Our findings offer a practical solution to address critical challenges in reliable transportation of goods, with potential implications for various fields in physical, engineering, and life sciences.

Tunable thermal conduction force without macroscopic temperature gradients.

Ubiquitous thermal conduction makes its force effect particularly important in diverse fields, such as electronic engineering and biochemistry. However, regulating thermal conduction force is still challenging due to two stringent restrictions. First, a temperature gradient is essential for inducing the force effect. Second, the force direction is fixed to the temperature gradient in a specific material. Here, we demonstrate that thermal conduction force can exist unexpectedly at a zero average temperature gradient in dielectric crystals. The wavelike feature of thermal conduction is considered, i.e., the second sound mode. Based on the momentum conservation law for phonon gases, we analyze thermal conduction force with the plane, zeroth-order Bessel, and first-order Bessel second sounds. Remarkably, the force direction is highly tunable to be along or against the second sound direction. These results provide valuable insights into thermal conduction force in those environments with temperature fluctuations, and they open up possibilities for practical applications in manipulating the local thermal conductivity of crystals.

Phononic band gap in random spring networks.

We investigate the relation between topological and vibrational properties of networked materials by analyzing, both numerically and analytically, the properties of a random spring network model. We establish a pseudodispersion relation, which allows us to predict the existence of distinct transitions from extended to localized vibrational modes in this class of materials. Consequently, we propose an alternative method to control phonon and elastic wave propagation in disordered networks. In particular, the phonon band gap of our spring network model can be enhanced by either increasing its average degree or decreasing its assortativity coefficient. Applications to phonon band engineering and vibrational energy harvesting are briefly discussed.

In situ Simulation of Thermal Reality.

Simulated reality encompasses virtual, augmented, and mixed realities-each characterized by different degrees of truthfulness in the visual perception: "all false," "coexistence of true and false," and "difficult distinction between true and false," respectively. In all these technologies, however, the temperature rendering of virtual objects is still an unsolved problem. Undoubtedly, the lack of thermal tactile functions substantially reduces the quality of the user's real-experience perception. To address this challenge, we propose theoretically and realize experimentally a technological platform for the in situ simulation of thermal reality. To this purpose, we design a thermal metadevice consisting of a reconfigurable array of radiating units, capable of generating the thermal image of any virtual object, and thus rendering it in situ together with its thermal signature. This is a substantial technological advance, which opens up new possibilities for simulated reality and its applications to human activities.