Lattice-Disordered High-Entropy Alloy Engineered by Thermal Dezincification for Improved Catalytic Hydrogen Evolution Reaction.

A disordered crystal structure is an asymmetrical atomic lattice resulting from the missing atoms (vacancies) or the lattice misarrangement in a solid-state material. It has been widely proven to improve the electrocatalytic hydrogen evolution reaction (HER) process. In the present work, due to the special physical properties (the low evaporation temperature of below 900 °C), Zn is utilized as a sacrificial component to create senary PtIrNiCoFeZn high-entropy alloy (HEA) with highly disordered lattices. The structure of the lattice-disordered PtIrNiCoFeZn HEA is characterized by the thermal diffusion scattering (TDS) in transmission electron microscope. Density functional theory calculations reveal that lattice disorder not only accelerates both the Volmer step and Tafel step during the HER process but also optimizes the intensity and distribution of projected density of states near the Fermi energy after the H2O and H adsorption. Anomalously high alkaline HER activity and stability are proven by experimental measurements. This work introduces a novel approach to preparing irregular lattices offering highly efficient HEA and a TDS characterization method to reveal the disordered lattice in materials. It provides a new route toward exploring and developing the catalytic activities of materials with asymmetrically disordered lattices.

Influence mechanism of the temporal duration of laser irradiation on photoacoustic technique: a review.

Significance: In the photoacoustic (PA) technique, the laser irradiation in the time domain (i.e., laser pulse duration) governs the characteristics of PA imaging-it plays a crucial role in the optical-acoustic interaction, the generation of PA signals, and the PA imaging performance. Aim: We aim to provide a comprehensive analysis of the impact of laser pulse duration on various aspects of PA imaging, encompassing the signal-to-noise ratio, the spatial resolution of PA imaging, the acoustic frequency spectrum of the acoustic wave, the initiation of specific physical phenomena, and the photothermal-PA (PT-PA) interaction/conversion. Approach: By surveying and reviewing the state-of-the-art investigations, we discuss the effects of laser pulse duration on the generation of PA signals in the context of biomedical PA imaging with respect to the aforementioned aspects. Results: First, we discuss the impact of laser pulse duration on the PA signal amplitude and its correlation with the lateral resolution of PA imaging. Subsequently, the relationship between the axial resolution of PA imaging and the laser pulse duration is analyzed with consideration of the acoustic frequency spectrum. Furthermore, we examine the manipulation of the pulse duration to trigger physical phenomena and its relevant applications. In addition, we elaborate on the tuning of the pulse duration to manipulate the conversion process and ratio from the PT to PA effect. Conclusions: We contribute to the understanding of the physical mechanisms governing pulse-width-dependent PA techniques. By gaining insight into the mechanism behind the influence of the laser pulse, we can trigger the pulse-with-dependent physical phenomena for specific PA applications, enhance PA imaging performance in biomedical imaging scenarios, and modulate PT-PA conversion by tuning the pulse duration precisely.

Temperature-induced migration of electro-neutral interacting colloidal particles.

Migration of colloidal particles induced by temperature gradients is commonly referred to as thermodiffusion, thermal diffusion, or the (Ludwig-)Soret effect. The thermophoretic force experienced by a colloidal particle that drives thermodiffusion consists of two distinct contributions: a contribution resulting from internal degrees of freedom of single colloidal particles, and a contribution due to the interactions between the colloids. We present an irreversible thermodynamics based theory for the latter collective contribution to the thermophoretic force. The present theory leads to a novel "thermophoretic interaction force" (for uncharged colloids), which has not been identified in earlier approaches. In addition, an N-particle Smoluchowski equation including temperature gradients is proposed, which complies with the irreversible thermodynamics approach. A comparison with experiments on colloids with a temperature dependent attractive interaction potential over a large concentration and temperature range is presented. The comparison shows that the novel thermophoretic interaction force is essential to describe data on the Soret coefficient and the thermodiffusion coefficient.

Diffusion-driven fabrication of calcium and phosphorous-doped zinc oxide heterostructures on titanium to achieve dual functions of osteogenesis and preventing bacterial infections.

Conventional Ti-based implants are vulnerable to postsurgical infection and improving the antibacterial efficiency without compromising the osteogenic ability is one of the key issues in bone implant design. Although zinc oxide (ZnO) nanorods grown on Ti substrates hydrothermally can improve the antibacterial properties, but cannot meet the stringent requirements of bone implants, as rapid degradation of ZnO and uncontrolled leaching of Zn2+ are detrimental to peri-implant cells and tissues. To solve these problems, a lattice-damage-free method is adopted to modify the ZnO nanorods with thin calcium phosphate (CaP) shells. The Ca and P ions from the CaP shells diffuse thermally into the ZnO lattice to prevent the ZnO nanorods from rapid degradation and ensure the sustained release of Zn2+ ions as well. Furthermore, the designed heterostructural nanorods not only induce the osteogenic performances of MC3T3-E1 cells but also exhibit excellent antibacterial ability against S. aureus and E. coli bacteria via physical penetration. In vivo studies also reveal that hybrid Ti-ZnO@CaP5 can not only eradicates bacteria in contact, but also provides sufficient biocompatibility without causing excessive inflammation response. Our study provides insights into the design of multifunctional biomaterials for bone implants. STATEMENT OF SIGNIFICANCE: • A lattice-damage-free method is adopted to modify the ZnO nanorods with thin calcium phosphate (CaP) shells. • The dynamic process of Ca and P diffusion into the ZnO lattice is analyzed by experimental verification and theoretical calculation. • The degradation rate of ZnO nanorods is significantly decreased after CaP deposition. • The ZnO nanorods after CaP deposition can not only sterilize bacteria in contact via physical penetration, but also provide sufficient biocompatibility and osteogenic capability without causing excessive inflammation response..

High-Performance Thermoelectric Flexible Ag2Se-Based Films with Wave-Shaped Buckling via a Thermal Diffusion Method.

Herein, an n-type Ag2Se thermoelectric flexible thin film has been fabricated on a polyimide (PI) substrate via a novel thermal diffusion method, and the thermoelectric performance is well-optimized by adjusting the pressure and temperature of thermal diffusion. All of the Ag2Se films are beneficial to grow (013) preferred orientations, which is conducive to performing a high Seebeck coefficient. By increasing the thermal diffusion temperature, the electrical conductivity can be rationally regulated while maintaining the independence of the Seebeck coefficient, which is mainly attributed to the increased electric mobility. As a result, the fabricated Ag2Se thin film achieves a high power factor of 18.25 µW cm-1 K-2 at room temperature and a maximum value of 21.7 µW cm-1 K-2 at 393 K. Additionally, the thermal diffusion method has resulted in a wave-shaped buckling, which is further verified as a promising structure to realize a larger temperature difference by the simulation results of finite element analysis (FEA). Additionally, this unique surface morphology of the Ag2Se thin film also exhibits outstanding mechanical properties, for which the elasticity modulus is only 0.42 GPa. Finally, a flexible round-shaped module assembled with Sb2Te3 has demonstrated an output power of 166 nW at a temperature difference of 50 K. This work not only introduces a new method of preparing Ag2Se thin films but also offers a convincing strategy of optimizing the microstructure to enhance low-grade heat utilization efficiency.

Successful treatment of eyebrow intradermal nevi by shearing combined with electrocautery and curettage: Two case reports.

BACKGROUND: An intradermal nevus is a common skin tumour, and the classical method of removal has a risk of recurrence and scarring. It is a challenge for dermatologists to treat eyebrow intradermal nevi quickly and efficiently. This study focused on investigating the efficacy and safety of shearing combined with electrocautery and curettage in the treatment of eyebrow intradermal nevi. CASE SUMMARY: We describe two adult patients with eyebrow intradermal nevi treated by shearing combined with electrocautery and curettage. Both patients were followed up regularly after surgery. At follow-up, no recurrence of eyebrow intradermal nevus and no obvious scars or hypopigmentation were found in either patient. The results indicated that shearing combined with electrocautery and curettage could remove eyebrow intradermal nevus without side effects and confirmed the efficacy and safety of this modality for treating these skin lesions. CONCLUSION: Shearing combined with electrocautery and curettage has superior merits, including simple operation, good cosmetic effects, and high patient satisfaction, presenting great application potential for treating intracutaneous nevus.

Interface Healing Between Adjacent Tracks in Fused Filament Fabrication Using In-Process Laser Heating.

Fused filament fabrication is one of the most desired thermal plastic additive manufacturing processes because of its ability to fabricate complex objects with high accessibility. However, due to the extrusion track-based direct write process mechanism, parts built using this method exhibit anisotropic mechanical properties. In this work, an in-process laser heating method is introduced to heal interface adhesion between adjacent deposited tracks by increasing the interface temperature to promote polymer reptation and enhance bonding strength of the interface of adjacent tracks. With the use of laser heating induced interface healing, the measured flexural strength between adjacent tracks in the same layer increased and exceeded that of the control sample tested along the track direction. The effect of laser on interface healing was also verified by investigating the load-displacement curve and morphology analysis of the fractured surface.

High Refractive Index GRIN Lens for IR Optics.

Infrared gradient refractive index (GRIN) material lenses have attracted much attention due to their continuously varying refractive index as a function of spatial coordinates in the medium. Herein, a glass accumulation thermal diffusion method was used to fabricate a high refractive index GRIN lens. Six Ge17.2As17.2SexTe(65-x) (x = 10.5-16) glasses with good thermal stability and high refractive index (n@10 µm > 3.1) were selected for thermal diffusion. The refractive index span (∆n) of 0.12 was achieved in this GRIN lens. After thermal diffusion, the lens still had good transmittance (45%) in the range of 8-12 µm. Thermal imaging confirmed that this lens can be molded into the designed shape. The refractive index profile was indirectly characterized by the structure and composition changes. The structure and composition variation became linear with the increase in temperature from 260 °C to 270 °C for 12 h, indicating that the refractive index changed linearly along the axis. The GRIN lens with a high refractive index could find applications in infrared optical systems and infrared lenses for thermal imaging.

Photoacoustic Characterization of TiO2 Thin-Films Deposited on Silicon Substrate Using Neural Networks.

In this paper, the possibility of determining the thermal, elastic and geometric characteristics of a thin TiO2 film deposited on a silicon substrate, with a thickness of 30 µm, in the frequency range of 20 to 20 kHz with neural networks were analysed. For this purpose, the geometric (thickness), thermal (thermal diffusivity, coefficient of linear expansion) and electronic parameters of substrates were known and constant in the two-layer model, while the following nano-layer thin-film parameters were changed: thickness, expansion and thermal diffusivity. Predictions of these three parameters of the thin-film were analysed separately with three neural networks. All of them together were joined by a fourth neural network. It was shown that the neural network, which analysed all three parameters at the same time, achieved the highest accuracy, so the use of networks that provide predictions for only one parameter is less reliable. The obtained results showed that the application of neural networks in determining the thermoelastic properties of a thin film on a supporting substrate enables the estimation of its characteristics with great accuracy.

Invasive Neuromonitoring Modalities in the Pediatric Population.

Invasive neuromonitoring has become an important part of pediatric neurocritical care, as neuromonitoring devices provide objective data that can guide patient management in real time. New modalities continue to emerge, allowing clinicians to integrate data that reflect different aspects of cerebral function to optimize patient management. Currently, available common invasive neuromonitoring devices that have been studied in the pediatric population include the intracranial pressure monitor, brain tissue oxygenation monitor, jugular venous oximetry, cerebral microdialysis, and thermal diffusion flowmetry. In this review, we describe these neuromonitoring technologies, including their mechanisms of function, indications for use, advantages and disadvantages, and efficacy, in pediatric neurocritical care settings with respect to patient outcomes.

Higher-Order Topological States in Thermal Diffusion.

Unlike conventional topological materials that carry topological states at their boundaries, higher-order topological materials are able to support topological states at boundaries of boundaries, such as corners and hinges. While band topology has been recently extended into thermal diffusion for thermal metamaterials, its realization is limited to a 1D thermal lattice, lacking access to the higher-order topology. In this work, the experimental realization is reported of a higher-order thermal topological insulator in a generalized 2D diffusion lattice. The topological corner states for thermal diffusion are observed in the bandgap of diffusion rate of the bulk, as a consequence of the anti-Hermitian nature of the diffusion Hamiltonian. The topological protection of these thermal corner states is demonstrated with the stability of their diffusion profile in the presence of amorphous deformation. This work constitutes the first realization of higher-order topology in purely diffusive systems and opens the door for future thermal management with topological protection beyond 1D geometries.

High-Efficiency Carbon-based CsPbI2 Br Perovskite Solar Cells from Dual Direction Thermal Diffusion Treatment with Cadmium Halides.

In recent years, carbon-based CsPbI2 Br perovskite solar cells (PSCs) have attracted more attention due to their low cost and good stability. However, the power conversion efficiency (PCE) of carbon-based CsPbI2 Br PSCs is still no more than 16%, because of the defects in CsPbI2 Br or at the interface with the electron transport layer (ETL), as well as the energy level mismatch, which lead to the loss of energy, thus limiting PCE values. Herein, a series of cadmium halides are introduced, including CdCl2 , CdBr2 and CdI2 for dual direction thermal diffusion treatment. Some Cd2+ ions thermally diffuse downward to passivate the defects inside or on the surface of SnO2 ETL. Meanwhile, the energy level structure of SnO2 ETL is adjusted, which is in favor of the transfer of electron carriers and blocking holes. On the other hand, part of Cd2+ and Cl- ions thermally diffuse upward into the CsPbI2 Br lattice to passivate crystal defects. Through dual direction thermal diffusion treatment by CdCl2 , CdI2 and CdBr2 , the performance of devices has been significantly improved, and their PCE has been increased from 13.01% of the original device to 14.47%, 14.31%, and 13.46%, respectively. According to existing reports, 14.47% is one of the highest PCE of carbon-based CsPbI2 Br PSCs with SnO2 ETLs.

Response of thermal conductivity of loess after high temperature in northern Shaanxi burnt rock area, China.

Spontaneous combustion of coal seams can produce a high temperature of about 800 ℃, which greatly changes the thermal conductivity of the overlying loess layer. The thermal conductivity of loess plays an important role in ecological restoration design and the calculation of roadbed and slope stability. In this study, loess in northern Shaanxi, China was taken as the research object to measure the mass-loss rate and heat conduction parameters of loess specimens after high temperature. The test results show that, between 23 and 900 °C, with temperature increasing, the mass-loss rate is reduced. And the heat conduction coefficient (λ), specific heat capacity (c), and thermal diffusion coefficient (α) decreased by 48.9%, 23.1%, and 35.6%. This is due to the air thermal resistance effect caused by the increase of pores and cracks in loess specimens after high temperature.

Estudo fotoacústico de dentes humanos submetidos à radioterapia / Photoacustic study of human teeth submitted to radiotherapy

Objetivo: Esta pesquisa teve como objetivo a caracterização, pela técnica de Espectroscopia de Absorção Fotoacústica, do efeito da radiação X sobre os tecidos dentais humanos mineralizados, irradiados com doses usada para tratamento de pacientes portadores de câncer de cabeça e pescoço. Materiais e métodos: As radiações foram fornecidas por um acelerador linear em dentes humanos seccionados longitudinalmente, onde a porção central foi investigada em três regiões: esmalte, dentina coronária e dentina cervical, antes e após as irradiações. 20 dentes foram analisados, onde um grupo formado por 10 dentes foi irradiado com dose total de 70 Gy fracionada em doses diárias de 2 Gy, enquanto outro grupo também com 10 dentes foi irradiado com uma dose única de 70 Gy. Resultados: Após a irradiação, foi observada uma redução significativa na difusividade térmica de 47 e 40% no esmalte, 43 e 37% na dentina coronária e 60 e 48% na dentina cervical, para a radiação em dose fracionada e única, respectivamente. Discussão: As medições da difusividade térmica das regiões analisadas, antes de serem irradiadas, mostraram que os valores encontrados estão de acordo com a literatura, enquanto que a forte queda da difusividade mostrou uma degradação da estrutura dentária. Além disso, a aplicação da radiação X gerou danos significativos ao dente que podem propiciar a for-mação e propagação das cáries de radiação. Conclusão: A redução da difusividade térmica observada retarda tanto a dissipação do calor, quanto a velocidade que este atinge as regiões internas do dente, levando a um retardo na sensação da dor, podendo acarretar no uso excessivo de energia durante os procedimentos odontológicos.

Aim: This research aimed to characterize, by the technique of Photoacoustic Absorption Spectroscopy, the effect of X-radiation on mineralized human dental tissues, irra-diated with doses used for the treatment of patients with head and neck cancer. Materials and methods: Radiation was introduced by a linear accelerator in humans teeth longitudinally sectioned, where the central portion was investigated in three regions: enamel, coronary dentin and cervical dentin, before and after irradiation. 20 teeth where analyzed, where a group formed by 10 teeth was irradiated with a total dose of 70 Gy, divided into daily doses of 2 Gy, while another group, also with 10 teeth, was irradiated with a single dose of 70 Gy. Results: After irradiation, a significant reduction in thermal diffusivity of 47 and 40% in enamel, 43 and 37% in coronary dentin and 60 and 48% in cervical dentin was observed for radiation in fractional and single doses, respectively. Discussion: The measures, obtained before the radiation, of thermal diffusivity on the analyzed regions, showed that the values found in this work are in agreement with the literature, while the strong fall in the thermal diffusivity showed that a degradation in the dental structure happened. In addition, the application of X radiation caused significant damage to the tooth that could promote the formation and propagation of radiation caries. Conclusion: The reduction in thermal diffusivity observed slows down both heat dissipation and the speed at which it reaches the internal regions of the tooth, leading to a delay in the sensation of pain, which may result in excessive energy usage during dental procedures.

Complementary Experimental Methods to Obtain Thermodynamic Parameters of Protein Ligand Systems.

In recent years, thermophoresis has emerged as a promising tool for quantifying biomolecular interactions. The underlying microscopic physical effect is still not understood, but often attributed to changes in the hydration layer once the binding occurs. To gain deeper insight, we investigate whether non-equilibrium coefficients can be related to equilibrium properties. Therefore, we compare thermophoretic data measured by thermal diffusion forced Rayleigh scattering (TDFRS) (which is a non-equilibrium process) with thermodynamic data obtained by isothermal titration calorimetry (ITC) (which is an equilibrium process). As a reference system, we studied the chelation reaction between ethylenediaminetetraacetic acid (EDTA) and calcium chloride (CaCl2) to relate the thermophoretic behavior quantified by the Soret coefficient ST to the Gibb's free energy ΔG determined in the ITC experiment using an expression proposed by Eastman. Finally, we have studied the binding of the protein Bovine Carbonic Anhydrase I (BCA I) to two different benzenesulfonamide derivatives: 4-fluorobenzenesulfonamide (4FBS) and pentafluorobenzenesulfonamide (PFBS). For all three systems, we find that the Gibb's free energies calculated from ST agree with ΔG from the ITC experiment. In addition, we also investigate the influence of fluorescent labeling, which allows measurements in a thermophoretic microfluidic cell. Re-examination of the fluorescently labeled system using ITC showed a strong influence of the dye on the binding behavior.

Cross-Sectional Profile Evolution of Cu-Ti Gradient Films on C17200 Cu by Vacuum Thermal Diffusion.

To improve the wear resistance and fatigue life of Cu alloys, surface modification by combining the magnetron sputtering of Ti film followed by vacuum thermal diffusion is always applied, where the structure and composition of the fabricated film play a determinant role on the mechanical properties. In the present work, the evolution of the layered structure and the element distribution of the formed multi-phases coating on C17200 Cu alloy are investigated by mathematical calculation based on Fick's law, and the experimental verification by the thermal diffusion of the gradient Cu-Ti film was undertaken under different temperatures and durations. The results show that the layered structure of the fabricated coating is dependent on the Cu-Ti atom concentration, the increasing time and the temperature, where a single or stratified layer is formed due to the generated Cu-Ti intermetallics for the inter-diffusion between the Cu and Ti atoms. The atom distribution by the proposed simulation method based on Fick's law corresponds to the experimental results, which can be applied to designing the structure of the modification layer.

Observation of Topological Edge States in Thermal Diffusion.

Topological band theory predicts that bulk materials with nontrivial topological phases support topological edge states. This phenomenon is universal for various wave systems and is widely observed for electromagnetic and acoustic waves. Here, the notion of band topology is extended from wave to diffusion dynamics. Unlike wave systems that are usually Hermitian, diffusion systems are anti-Hermitian with purely imaginary eigenvalues corresponding to decay rates. By direct probe of the temperature diffusion, the Hamiltonian of a thermal lattice is experimentally retrieved, and the emergence of topological edge decays is observed within the gap of bulk decays. The results of this work show that such edge states exhibit robust decay rates, which are topologically protected against disorder. This work constitutes a thermal analogue of topological insulators and paves the way to exploring defect-immune heat dissipation.

A New Nonlinear Photothermal Iterative Theory for Port-Wine Stain Detection.

The development of appropriate photothermal detection of skin diseases to meet complex clinical demands is an urgent challenge for the prevention and therapy of skin cancer. An extensive body of literature has ignored all high-order harmonics above the second order and their influences on low-order harmonics. In this paper, a new iterative numerical method is developed for solving the nonlinear thermal diffusion equation to improve nonlinear photothermal detection for the noninvasive assessment of the thickness of port-wine stain (PWS). First, based on the anatomical and structural properties of skin tissue of PWS, a nonlinear theoretical model for photothermal detection is established. Second, a corresponding nonlinear thermal diffusion equation is solved by using the new iterative numerical method and taking into account harmonics above the second-order and their effects on lower-order harmonics. Finally, the thickness and excitation light intensity of PWS samples are numerically simulated. The simulation results show that the numerical solution converges fasterand the physical meaning of the solution is clearerwith the new method than with the traditional perturbation method. The rate of change in each harmonic with the sample thickness for the new method is higher than that for the conventional perturbation method, suggesting that the proposed numerical method may provide greater detection sensitivity. The results of the study provide a theoretical basis for the clinical treatment of PWS.

Entropy Generation during Head-On Interaction of Premixed Flames with Inert Walls within Turbulent Boundary Layers.

The statistical behaviours of different entropy generation mechanisms in the head-on interaction of turbulent premixed flames with a chemically inert wall within turbulent boundary layers have been analysed using Direct Numerical Simulation data. The entropy generation characteristics in the case of head-on premixed flame interaction with an isothermal wall is compared to that for an adiabatic wall. It has been found that entropy generation due to chemical reaction, thermal diffusion and molecular mixing remain comparable when the flame is away from the wall for both wall boundary conditions. However, the wall boundary condition affects the entropy generation during flame-wall interaction. In the case of isothermal wall, the entropy generation due to chemical reaction vanishes because of flame quenching and the entropy generation due to thermal diffusion becomes the leading entropy generator at the wall. By contrast, the entropy generation due to thermal diffusion and molecular mixing decrease at the adiabatic wall because of the vanishing wall-normal components of the gradients of temperature and species mass/mole fractions. These differences have significant effects on the overall entropy generation rate during flame-wall interaction, which suggest that combustor wall cooling needs to be optimized from the point of view of structural integrity and thermodynamic irreversibility.

Observation of Weyl exceptional rings in thermal diffusion.

SignificanceThermal diffusion is dissipative and strongly related to non-Hermitian physics. At the same time, non-Hermitian Weyl systems have spurred tremendous interest across photonics and acoustics. This correlation has been long ignored and hence shed little light upon the question of whether the Weyl exceptional ring (WER) in thermal diffusion could exist. Intuitively, thermal diffusion provides no real parameter dimensions, thus prohibiting a topological nature and WER. This work breaks this perception by imitating synthetic dimensions via two spatiotemporal advection pairs. The WER is achieved in thermal diffusive systems. Both surface-like and bulk states are demonstrated by coupling two WERs with opposite topological charges. These findings extend topological notions to diffusions and motivate investigation of non-Hermitian diffusive and dissipative control.