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Featured Application: The dimensionless nonlinear model can be modified to the qualitative dynamic analysis of the heated systems with different supercritical fluids under external vertical accelerations. Employing the external force method to regard seismic impact and the three-region methodology to analyze the supercritical heated channel, a non-linear dynamic model was developed to investigate the transient characteristics of single channel or parallel channels under the impacts of vertical sinusoidal and seismic accelerations. The present model was validated against the experimental data, which could suitably estimate the additional pressure drop caused by the vertical vibrations. The influences of parameters on the seismic-induced oscillation conducted in a supercritical heated channel indicated that a longer heated length, uprating operation power and a larger outlet loss coefficient all exhibit unstable effects, while the increase of inlet loss coefficient, a larger tube diameter and a lower inlet fluid temperature would tend to stabilize the system. Moreover, the supercritical fluid would present a high natural frequency in the very small NP-SUB region. The parametric effects on the parallel channel system are related to the inherent stability nature of initial state and the interactions among channels. The more uneven heat flux distribution among channels would cause a larger vibration-induced oscillation. In particular, when it is combined with the resonance effect, the system may exhibit much larger oscillations than in the case of non-resonance. [ABSTRACT FROM AUTHOR]

In this study, experimental tests were carried out to investigate the feasibility of heat transfer enhancement by ultrasonic vibration under a subcooled pool condition. A commercial stainless-steel heater was utilized along with a water tank, and three ultrasonic transducers were attached underneath the tank bottom to generate ultrasonic vibration with a frequency of 40 kHz and total power of 150 W. For demonstrating the effectiveness, the tests were performed with and without ultrasonic vibration under a constant water temperature of 30°C and pressure of 1 atm. The heights of heater were set at 15, 22, and 33 mm from the tank bottom, and the heat flux was operated from 7800 to 70800 W/m2, which covered the regimes of single phase natural convection and subcooled nucleate boiling. Instantaneous signals of temperature and heat flux were recorded during the experiment, and the heat transfer coefficients were determined for each condition. The results show that the heat transfer coefficient can increase up to 3880 W/m2K and the enhancement ratio can reach up to 284% by ultrasonic vibration. Trends of heat transfer increments and enhancement ratios against heat flux and height were presented. This study successfully demonstrated the feasibility of heat transfer enhancement by ultrasonic vibrations. [ABSTRACT FROM AUTHOR]

An experimental study on air-water two-phase flow under vibration condition has been conducted using double-sensor conductivity probe. The test section is an annular geometry with hydraulic diameter of 19.1 mm. The vibration frequency ranges from 0.47 Hz to 2.47 Hz. Local measurements of void fraction, interfacial area concentration (IAC), and Sauter mean diameter have been performed along one radius in the vibration direction. The result shows that local parameters fluctuate continuously around the base values in the vibration cycle. Additional bubble force due to inertia is used to explain lateral bubble motions. The fluctuation amplitudes of local void fraction and IAC increase significantly with vibration frequency. The radial distribution of local parameters at the maximum vibration displacement is specifically analyzed. In the void fraction and IAC profiles, the peak near the inner wall is weakened or even disappearing and a strong peak skewed to outer wall is gradually observed with the increase of vibration frequency. The nondimensional peak void fraction can reach a maximum of 49% and the mean relative variation of local void fraction can increase to more than 29% as the vibration frequency increases to 2.47 Hz. But the increase of vibration frequency does not bring significant change to bubble diameter. [ABSTRACT FROM AUTHOR]

The technique of laser-assisted nanoimprinting lithography (LAN) has been proposed to utilize an excimer laser to irradiate through a quartz mold and melts a thin polymer film on the substrate for micro- to nano-scaled fabrications. This study introduces optical multiple reflection theory to demonstrate both analytical and numerical modeling during the LAN process and to predict the thermal response theoretically. Furthermore, the capability of energy absorption for polymer resist is examined herein. The temperature of polymer resist with the capability of energy absorption is much higher than that without energy absorption. This study demonstrates the characteristics of the energy absorption for polymer materials could improve the performance of the LAN process for the reason that the thermally affected region is extremely limited. [ABSTRACT FROM AUTHOR]

Abstract: Micro-grooves with various feature sizes ranged form 200 to 500μm were fabricated as micro-wick structures by two different processes, including chemical etching and precision milling, for the experimental investigation and visualization on capillary and boiling limits. Pure water was employed as the working fluid, and the surfaces of the micro-wick structures were cleaned to ensure the hydrophile and the same surface conditions of these samples before testing. Various heat fluxes were then applied to these micro-wick structures to measure their thermal performances and capillary and boiling limits by both temperature measurement and experimental visualization. In addition, the experimental results were compared with the simplified analytical models. This study proposes a simple method to determine working limits and thermal performance of micro-structures for designing wick and selecting process. [Copyright &y& Elsevier]

In the title compound, C30H28N2S4, the S—S bond length is 1.9910 (13) Å. In the absence of classical hydrogen bonds and π–π inter­actions, the crystal packing is stabilized by van der Waals forces. [ABSTRACT FROM AUTHOR]

Quantum geometry in condensed-matter physics has two components: the real part quantum metric and the imaginary part Berry curvature. Whereas the effects of Berry curvature have been observed through phenomena such as the quantum Hall effect in two-dimensional electron gases and the anomalous Hall effect (AHE) in ferromagnets, the quantum metric has rarely been explored. Here, we report a nonlinear Hall effect induced by the quantum metric dipole by interfacing even-layered MnBi 2 Te 4 with black phosphorus. The quantum metric nonlinear Hall effect switches direction upon reversing the antiferromagnetic (AFM) spins and exhibits distinct scaling that is independent of the scattering time. Our results open the door to discovering quantum metric responses predicted theoretically and pave the way for applications that bridge nonlinear electronics with AFM spintronics.

Background: Wild rats have the potential to hold zoonotic infectious agents that can spread to humans and cause disease., Aim: To better understand the composition of gut bacterial communities in rats is essential for preventing and treating such diseases. As a tropical island located in the south of China, Hainan province has abundant rat species. Here, we examined the gut bacterial composition in wild adult rats from Hainan province., Methods: Fresh fecal samples were collected from 162 wild adult rats, including three species ( Rattus norvegicus , Leopoldamys edwardsi , and Rattus losea ), from nine regions of Hainan province between 2017-2018., Results: We analyzed the composition of gut microbiota using the 16S rRNA gene amplicon sequencing. We identified 4903 bacterial operational taxonomic units (30 phyla, 175 families, and 498 genera), which vary between samples of different rat species in various habitats at various times of the year. In general, Firmicutes were the most abundant phyla, followed by Bacteroidetes (15.55%), Proteobacteria (6.13%), and Actinobacteria (4.02%). The genus Lactobacillus (20.08%), unidentified_ Clostridiales (5.16%), Romboutsia (4.33%), unidentified_ Ruminococcaceae (3.83%), Bacteroides (3.66%), Helicobacter (2.40%) and Streptococcus (2.37%) were dominant., Conclusion: The composition and abundance of the gut microbial communities varied between rat species and locations. This work provides fundamental information to identify microbial communities useful for disease control in Hainan province., Competing Interests: Conflict-of-interest statement: All the authors report no relevant conflicts of interest for this article., (©The Author(s) 2023. Published by Baishideng Publishing Group Inc. All rights reserved.)

At low temperature, a thermodynamic system undergoes a phase transition when a physical parameter passes through a singularity point of the free energy. This corresponds to the formation of a new order. At high temperature, thermal fluctuations destroy the order. Correspondingly, the free energy is a smooth function of the physical parameter and singularities only occur at complex values of the parameter. Since a complex valued parameter is unphysical, no phase transitions are expected when the physical parameter is varied. Here we show that the quantum evolution of a system, initially in thermal equilibrium and driven by a designed interaction, is equivalent to the partition function of a complex parameter. Therefore, we can access the complex singularity points of thermodynamic functions and observe phase transitions even at high temperature. We further show that such phase transitions in the complex plane are related to topological properties of the renormalization group flows of the complex parameters. This result makes it possible to study thermodynamics in the complex plane of physical parameters.

Central spin decoherence is useful for detecting many-body physics in environments and moreover, the spin echo control can remove the effects of static thermal fluctuations so that the quantum fluctuations are revealed. The central spin decoherence approach, however, is feasible only in some special configurations and often requires uniform coupling between the central spin and individual spins in the baths, which are very challenging in experiments. Here, by making analogue between central spin decoherence and depolarization of photons, we propose a scheme of Faraday rotation echo spectroscopy (FRES) for studying quantum fluctuations in interacting spin systems. The echo control of the photon polarization is realized by flipping the polarization with a birefringence crystal. The FRES, similar to spin echo in magnetic resonance spectroscopy, can suppress the effects of the static magnetic fluctuations and therefore reveal dynamical magnetic fluctuations. We apply the scheme to a rare-earth compound LiHoF4 and calculate the echo signal, which is related to the quantum fluctuations of the system. We observe enhanced signals at the phase boundary. The FRES should be useful for studying quantum fluctuations in a broad range of spin systems, including cold atoms, quantum dots, solid-state impurities, and transparent magnetic materials.

Purpose: The purpose of this work was to evaluate the absorbed dose to AL2O3 dosimeter at various depths of water phantom in radiotherapy photon beams by Monte Carlo simulation and evaluate the beam quality dependence., Methods: The simulations were done using EGSnrc. The cylindrical Al2O3 dosimeter (Phi4 mm x 1 mm) was placed at the central axis of the water phantom (Phi16 cm x 16 cm) at depths between 0.5 and 8 cm. The incident beams included monoenergetic photon beams ranging from 1 to 18 MeV, 60Co gamma beams, Varian 6 MV beams using phase space files based on a full simulation of the linac, and Varian beams between 4 and 24 MV using Mohan's spectra. The absorbed dose to the dosimeter and the water at the corresponding position in the absence of the dosimeter, as well as absorbed dose ratio factor fmd, was calculated., Results: The results show that fmd depends obviously on the photon energy at the shallow depths. However, as the depth increases, the change in fmd becomes small, beyond the buildup region, the maximum discrepancy of fmd to the average value is not more than 1%., Conclusions: These simulation results confirm the use of Al2O3 dosimeter in radiotherapy photon beams and clearly indicate that more attention should be paid when using such a dosimeter in the buildup region of high-energy radiotherapy photon beams.