bluuebunny/crossref_metadata_2025 huggingface dataset:
Hankel determinant and orthogonal polynomials for a perturbed Gaussian weight: From finite n to large n asymptotics
Authors: Min Chao , Chen Yang
Published: August 2023

We study the monic polynomials Pn(x; t), orthogonal with respect to a symmetric perturbed Gaussian weight function w(x)=w(x;t)≔e−x21+tx2λ,x∈R, with t>0,λ∈R. This problem is related to single-user multiple-input multiple-output systems in information theory. It is shown that the recurrence coefficient βn(t) is related to a particular Painlevé V transcendent, and the sub-leading coefficient p(n, t) of Pn(x; t) (Pn(x; t) = xn + p(n, t)xn−2 + ⋯) satisfies the Jimbo–Miwa–Okamoto σ-form of the Painlevé V equation. Furthermore, we derive the second-order difference equations satisfied by βn(t) and p(n, t), respectively. This enables us to obtain the large n full asymptotic expansions for βn(t) and p(n, t) with the aid of Dyson’s Coulomb fluid approach in the one-cut case [i.e., λt ≤ 1 (t > 0)]. We also consider the Hankel determinant Dn(t), generated by the perturbed Gaussian weight. It is found that Φn(t), a quantity allied to the logarithmic derivative of Dn(t) via Φn(t)=2t2ddtlnDn(t)−2nλt, can be expressed in terms of βn(t) and p(n, t). Based on this result, we obtain the large n asymptotic expansion of Φn(t) and then that of the Hankel determinant Dn(t) in the one-cut case.
Staticity of asymptotically hyperbolic minimal mass extensions
Authors: Martin Daniel
Published: August 2023

In this paper, we define the Bartnik mass of a domain whose boundary is connected and compact, has scalar curvature bounded below −n(n − 1), and whose extensions are asymptotically hyperbolic manifolds. With this definition, we show that asymptotically hyperbolic admissible extensions of a domain that achieve the Bartnik mass must admit a static potential. Given a non-static admissible extension of a domain, we are able to construct a one-parameter family of metrics that are close to the original metric, have smaller mass, share the same bound on the scalar curvature, and contain the domain isometrically.
Vortex-ultrasound for microbubble-mediated thrombolysis of retracted clots
Authors: Kim Howuk , Zhang Bohua , Wu Huaiyu , Yao Junjie , Shi Chengzhi , Jiang Xiaoning
Published: August 2023

Endovascular sonothrombolysis has gained significant attention due to its benefits, including direct targeting of the thrombus with sonication and reduced side effects. However, the small aperture of endovascular transducers restricts the improvement of their potential clinical efficiency due to inefficient acoustic radiation. Hence, in an earlier study, we used vortex ultrasound with an endovascular ultrasound transducer to induce shear stress and enhance the clot lysis. In this study, the vortex acoustic transduction mechanism was investigated using numerical simulations and hydrophone tests. Following this characterization, we demonstrated the performance of the vortex ultrasound transducer in thrombolysis of retracted clots in in vitro tests. The test results indicated that the maximum lysis rates were 79.0% and 32.2% with the vortex ultrasound for unretracted and retracted clots, respectively. The vortex ultrasound enhanced the efficiency of the thrombolysis by approximately 49%, both for retracted and unretracted clots, compared with the typical non-vortex ultrasound technique. Therefore, the use of endovascular vortex ultrasound holds promise as a potential clinical option for the thrombolysis of retracted clots.
Splashing of Sn–Bi–Ag solder droplets
Authors: Meza-Alarcon K. L. , Quetzeri-Santiago M. A. , Neri-Flores M. A. , del Río J. Antonio , Castrejón-Pita J. R.
Published: August 2023

In this paper, we study the behavior and spreading dynamics of molten metallic alloy droplets. Five solders, including three rare earth elements and a commercial alloy, were used to assess their splashing behavior in terms of the material and impact conditions. The metallic solders were melted down in a heated chamber (oven) and then dripped onto a smooth copper flat substrate as spherical droplets. The impact of each alloy droplet was recorded and analyzed by high-speed imaging and image analysis to obtain the impact speed, the droplet size, and the dynamic contact angle. Our results show that the impact behavior is well parameterized by the splashing ratio, a dimensionless number encompassing the impact and liquid properties, and the maximum dynamic spreading contact angle. Our results are useful to the industry as they provide a criterion to select the maximum soldering injection speed or the droplet size to avoid splashing during soldering or the jetting of molten metals.
Direct density modulation of photo-assisted field emission from an RF cold cathode
Authors: Jin Lan , Zhou Yang , Zhang Peng
Published: August 2023

This paper explores direct density modulation of high-current electron beam emission from an RF cold cathode using optical excitation. We theoretically study the photo-assisted field emission of periodically bunched electron beams of various pulse shapes under the combined excitation of an RF field and an optical field, using an exact quantum model. Both continuous-wave (CW) and pulsed optical fields are considered. The emission current pulse amplitude, pulse width, electron number density per pulse, as well as pulse shape and its harmonic contents are investigated in detail. For CW photon sources in the UV to NIR range (i.e., 200–1200 nm), increasing the optical intensity under an RF bias tends to change the current pulse from a Gaussian to sinusoidal-like shape, thus offering strong flexibility to control the frequency components in beam current emission. Pulsed photon sources combined with an RF field can produce sharp, high-current electron bunches with pulse duration comparable with or even less than that of the optical pulse. A contour map of the density modulation depth is constructed for different combinations of RF and laser fields. The results provide insight into unlocking new opportunities to achieve direct density modulation during electron current emission by optical means.
Ferroelectric Al1−xBxN thin films integrated on Si
Authors: Hayden John , Shepard Joseph , Maria Jon-Paul
Published: August 2023

Ferroelectric Al0.93B0.07N thin films are prepared (100) Si substrates. The necessary c-axis out-of-plane orientation to observe macroscopic ferroelectric switching was achieved by implementing an initial Ar/N2 plasma treatment, followed by a thin layer of AlN to initiate the desired texture and a 150 nm W layer. The plasma treatment facilitates crystallinity enhancement of the AlN template layer, allowing for subsequent growth of highly oriented W and Al0.93B0.07N layers. The W layer exhibits random in-plane orientation and exclusive (110) out-of-plane orientation with a rocking curve width of 1.4°. When grown on these W surfaces, 175 nm thick Al0.93B0.07N films exhibit random in-plane orientation and exclusive (001) texture with rocking curve full-width-half-max values of 1.6° and RMS roughness values less than 1 nm. Polarization hysteresis measurements show robust hysteresis with coercive field values of 5.4 MV/cm and remanent polarization values of 136 μC/cm2. XPS depth profile analysis suggests that the plasma treatment converts the existing native oxide to a nitrogen rich oxynitride with approximate composition Si3O0.5N3.67. Cross-sectional TEM reveals that the oxynitride interlayer is amorphous and ∼3.4 nm thick, more than double the native oxide thickness measured by multiwavelength ellipsometry, implying that (oxy)nitride growth continues after conversion of the native oxide. This new family of ferroelectric wurtzites is interesting from an integration perspective given their chemical compatibility with mainstream semiconductors. Developing synthesis routes that promote needed texture while preserving compatible processing windows is an important step toward practical integration.
Kinetic simulation of a 50 mTorr capacitively coupled argon discharge over a range of frequencies and comparison to experiments
Authors: Simha Saurabh , Sharma Sarveshwar , Khrabrov Alexander , Kaganovich Igor , Poggie Jonathan , Macheret Sergey
Published: August 2023

The effect of driving frequency in the range of 13.56–73 MHz on electron energy distribution and electron heating modes in a 50 mTorr capacitively coupled argon plasma discharge is studied using 1D-3V particle-in-cell simulations. Calculated electron energy probability functions exhibit three distinct “temperatures” for low-, mid-, and high-energy electrons at all the studied driving frequencies. When compared to published experimental data, the calculated probability functions show a reasonable agreement for the energy range resolved in the measurements (about 2–10 eV). Discrepancies due to limitations in experimental energy resolution outside this range lead to differences between computational and experimental values of the electron number density determined from the distribution functions, and the predicted effective electron temperature is within 25% of experimental values. The impedance of the discharge is interpreted in terms of a homogeneous equivalent circuit model, and the driving frequency dependence of the inferred combined sheath thickness is found to obey a known, theoretically derived, power law. The average power transferred from the field to the electrons (electron heating) is computed, and a region of negative heating near the sheath edge, particularly at higher driving frequencies, is identified. Analysis of the electron momentum equation shows that electron inertia, which on temporal averaging would be zero in a linear regime, is responsible for negative values of power deposition near the sheath edge at high driving frequencies due to the highly nonlinear behavior of the discharge.
Performance and stability improvement of CVD monolayer MoS2 transistors through HfO2 dielectrics engineering
Authors: Huang Chunhui , Yan Zeyi , Hu Chengwei , Xiong Xiong , Wu Yanqing
Published: August 2023

Monolayer molybdenum disulfide (MoS2) is a promising semiconductor channel material for future electronics due to its atomic thickness and high mobility. However, conventional back-gate MoS2 transistors suffer from substantial scattering caused by substrate and surface adsorbates, which impair carrier mobility and device reliability. In this work, we demonstrate an exemplary dielectric engineering approach that uses atomic-layer-deposited hafnium oxide (HfO2) as the gate dielectric and channel passivation layer to improve device performance and positive bias instability. The large-single-crystal monolayer MoS2 film was directly synthesized on SiO2/Si substrates by a low-pressure chemical vapor deposition method. MoS2 transistors with various dielectrics were fabricated and characterized for a fair comparison. The mobility increased from 4.2 to 19.9 cm2/V·s by suppressing charged impurities and phonon scattering when transferring the MoS2 channel from 100 nm SiO2 substrates to 20 nm HfO2 substrates. Passivation of another 10 nm HfO2 on the back-gate transistors further increased the mobility to 36.4 cm2/V·s with a high drive current of 107 μA/μm. Moreover, the threshold voltage shift of the passivated transistor was reduced by about 58% from 1.9 to 0.8 V under positive bias stress. This is due to the fact that channel passivation with HfO2 effectively eliminated charge trapping of adsorbed substances. These results reveal that HfO2 gate dielectric and passivation by atomic-layer deposition are effective methods to improve the performance and stability of MoS2 devices.
Intense nano-pulse stimulation-induced dynamic changes in vesicle trafficking visualized by super-resolution fluorescence microscopy
Authors: Guo Jinsong , Chen Congcong , Sun Zhenglong , Zhang Long , Li Hui , Wu Xiaodong , Zhuang Jie
Published: August 2023

Super-resolution fluorescence microscopy (SRFM) has revolutionized biomedical research by providing valuable information at the nanometer-scale within cells. Recent advances in SRFM enable researchers to probe dynamic processes in living cells with unprecedented spatiotemporal resolution. Vesicle trafficking plays a critical role in tumor proliferation and invasion. Understanding the dynamics of vesicle trafficking in cancer cells is essential for cancer therapy. This study visualized and quantified changes in vesicle trafficking dynamics in cancer cells induced by intense nano-pulse stimulation (NPS) using SRFM. As an emerging physical modality for cancer therapy, it remains unknown whether and how NPS affects vesicle trafficking during its interaction with cancer cells. Our results indicate that NPS decreases the number, velocity, and track length of vesicles while significantly increasing the average size of vesicles. Notably, vesicle trafficking between cancer cells and normal human lung bronchial epithelial cells was also inhibited. This study provides experimental evidence that NPS directly affects vesicle trafficking. Furthermore, the results of this study may shed light on a better understanding of the mechanism by which NPS inhibits cancer invasion and metastasis. Finally, this work provides a potential physical method to regulate vesicle transport.
Multiple-beam colloidal quantum dot lasers in a waveguide-grating-waveguide microcavity
Authors: Liu Fangyuan , Yin Tuyu , Liu Yu , Naeem Iqbal , Guo Dan , Cui Libin , Zhai Tianrui
Published: August 2023

In this work, multiple-beam colloidal quantum dot lasers are achieved in a double waveguide-grating (waveguide-grating-waveguide, W-G-W) microcavity. The grating is fabricated simply using interference lithography, and CdSe/CdS/ZnS colloidal quantum dots (CQDs) are spin-coated as the gain to form an active waveguide-grating structure. The photoresist film, which is not completely etched to the bottom, provides another waveguide-grating structure. In the W-G-W structure, low-threshold multiple-beam laser output is realized under optical pumping with emission peaks at 664.6 and 645.2 nm. The oblique laser is derived from a quasi-propagation mode. The thresholds of the two laser modes are 22.7 and 28.3 μJ/cm2, respectively, and both laser modes are TE0 modes. In addition, the emission wavelengths of the two modes of the designed distributed feedback laser can be flexibly tuned by changing the thickness of the CQDs' waveguide layer. The presence of quasi-propagation modes provides another method for designing compact laser sources, which could help in the design of wireless communication networks, hyperspectral 3D sensing, and color laser displays.
Dynamical behavior and transport coefficients of the pseudo hard-sphere fluid
Authors: Nicasio-Collazo Luz Adriana , Ramírez-Medina Carlos Alberto , Torres-Carbajal Alexis
Published: August 2023

In this work, we employ a recent approach to characterize the hard-sphere (HS) fluid by means of a continuous interaction potential, commonly referred to as pseudo hard-sphere potential, in order to determine HS transport coefficients as a function of the volume fraction for the three-dimensional mono disperse fluid. Using equilibrium molecular dynamics simulations, we determine time-dependent velocity, shear stress, and energy flux autocorrelation functions in order to use them within the Green–Kubo framework to compute the self-diffusion, shear viscosity, and thermal conductivity coefficients, respectively. Results are discussed as a function of the volume fraction and were compared to theoretical and simulations results previously reported by other authors. The main purpose of this work is twofold: first, testing the continuous approach of the HS fluid for the computation of dynamic properties and second, performing a systematic determination of aforementioned transport coefficients to analyze them as a function of fluid volume fraction. Furthermore, our results are used to provide a practical correction to the Chapman–Enskog equations for the HS self-diffusion, shear viscosity, and thermal conductivity predictions in a wide range of volume fractions.
Nanogenerator based self-powered motion monitoring for flapping wings of bio-inspired flying robots
Authors: Zheng Hao , Zeng Xu , Wang Yunfei , Wang Yan , Wang Zhonglai , Zhang Xiaosheng
Published: August 2023

Under the constraints of weight and power, achieving airborne monitoring of wings' flexible motion toward bio-inspired flying robots is an arduous challenge. Herein, we present a self-powered motion monitoring method based on nanogenerators to tackle this issue. First, a locally adaptable integration structure of triboelectric nanogenerator (TENG) integrated wings is proposed for the design of airborne devices. Second, a theoretical output model is developed to dynamically monitor the flapping motion of TENG-integrated wings. The proposed approach is a multi-target monitoring technique that enables the sensing of parameters, such as the flapping frequency and the flapping angles with stability. After validation, the monitoring error of the wing plane's pitch angle affected by device stability is less than 0.7°. Likewise, the maximum observed error rate for flapping frequency monitoring is about 0.1%. This technique will further enhance the intelligent airborne wing state perception for bio-inspired flying robots.
Rarefied gas–surface interaction under multi-incidence parameter coupling conditions: A molecular dynamics simulation
Authors: Miao Qing , Li Langquan , Pi Xingcai , Qiu Yue , Fang Ming
Published: August 2023

An effective gas–surface interaction model is crucial for accurately predicting the aerodynamic thermal properties of hypersonic vehicles. However, the applicability of classical interface models has been severely challenged under hypersonic conditions since the boundary properties predicted by different gas-surface interaction models vary greatly, which seriously threatens the flight safety. Therefore, in order to accurately describe gas–surface interaction under hypersonic conditions, we analyzed the reflection behavior of the gas on a silicon-based surface through molecular dynamics simulations and presented a modified Maxwell model. Furthermore, the dependence of model parameters on incident energy, angle, and gas type was also obtained. By analyzing gas–surface interaction time and potential well depth, the endogenous mechanism of the accommodation coefficient variation under multi-incidence parameter coupling conditions is revealed. These results not only elucidate the microscopic mechanism of gas–surface interaction but also provide an important basis for establishing accurate boundary conditions for larger-scale simulations.
The influence of roughness-element-spacing on turbulent entrainment over spanwise heterogeneous roughness
Authors: Long Yanguang , Wang Jinjun , Pan Chong
Published: August 2023

Spanwise heterogeneous surfaces have been found to modulate local turbulent entrainment by inducing large-scale secondary flows (SFs). This work aims to clarify the variations of the local and total entrainment fluxes with the intensity of SF. The SF intensity is controlled by the spanwise spacing between adjacent ridge-type roughness elements s. It is found that, for the two components of turbulent entrainment (nibbling and engulfment), their local fluxes grow rapidly with the SF intensity in the downwash regions; asymmetrically, both fluxes decline slowly and then become relatively stable in the upwash regions. In other words, the downwash flow is more effective in modulating the local entrainment flux than the upwash flow. Therefore, the largest total entrainment flux would be induced at s≈δ, where the SF intensity is the largest (δ is the boundary layer thickness). Moreover, the emergence of the tertiary flow when s≳2δ would lower the local entrainment flux, and reduce the total flux to the same level of the homogeneous roughness. Therefore, it is deduced that a heterogeneous surface with a large roughness-element spacing could not enhance the total entrainment flux.
Enhanced intensity of Raman signals from hexagonal boron nitride films
Authors: Schaumburg F. , Sleziona S. , Zöllner M. , Dergianlis V. , Schleberger M. , Geller M. , Lorke A. , Prinz G.
Published: August 2023

Optical spectroscopy is commonly used to study the properties of 2D materials. In order to obtain the best signal-to-noise ratio, it is important to optimize the incoupling of the excitation laser and, at the same time, reduce spurious light reflection. We performed Raman spectroscopy on exfoliated hexagonal boron nitride (hBN) flakes of different thicknesses, placed on a 300 nm SiO2 on Si substrate. By changing the hBN layer thickness, we found a specific thickness, where the Raman signals from the substrate and the hBN showed maximum intensity, whereas the backscattered laser light was suppressed. To explain the increased emission, we calculated the reflectivity and transmissivity of the full layer system (air, hBN, SiO2, and Si) as a function of hBN layer thicknesses for different excitation wavelengths (457, 532, and 633 nm), using the transfer-matrix algorithm. To compare theory with the experiment, we performed Raman measurements with these three different excitation wavelengths on different flakes and determined their thicknesses with AFM measurements. The experimental results are in good agreement with the calculations, which shows the importance of thin film interference to obtain optimum spectroscopic conditions. Since interference colors are easily visible in an optical microscope, this facilitates the choice of optimum flakes for a wide range of optical characterization techniques, including Raman, photoluminescence, and single defect spectroscopy.
Prediction of particle-laden pipe flows using deep neural network models
Authors: Haghshenas Armin , Hedayatpour Shiva , Groll Rodion
Published: August 2023

An accurate and fast prediction of particle-laden flow fields is of particular relevance for a wide variety of industrial applications. The motivation for this research is to evaluate the applicability of deep learning methods for providing statistical properties of the carrier and dispersed phases in a particle-laden vertical pipe flow. Deep neural network (DNN) models are trained for different dependent variables using 756 high-fidelity datasets acquired from point-particle large-eddy simulations for different values of Stokes number, St, bulk particle volume fraction, Φ¯v, and wall roughness, Δγ, for the range St=10−500, Φ¯v=5×10−5−10−3, and Δγ=1°−6°. The considered parameter space corresponds to the inertia-dominated regime and covers a large extent of the typical conditions in powder-based laser metal deposition. We find that the DNN models capture the nonlinear dynamics of the system and recreate the statistical properties of the particle-laden pipe flow. However, DNN predictions of the particle statistics are of higher accuracy compared to the fluid statistics, which is attributed to the highly non-monotonic dependence of the fluid statistics on the control parameters. Owing to significantly decreased time-to-solution, the trained DNN models are promising as surrogate models to expedite model development and design process of various industrial applications.
Soret-induced convection of ternary fluid in a horizontal porous layer heated from below
Authors: Lyubimova T. P. , Shubenkov I. S.
Published: August 2023

The present paper deals with the investigation of the Soret-induced convection of a three-component mixture of hydrocarbons in a horizontal porous layer. This problem is important for geological applications. The first part of the paper is devoted to the linear stability of the conductive state. The longwave instability is studied analytically by the expansion into the power series with respect to the wave number. A new long-wave oscillatory instability mode existing at negative separation ratios is found out. It is shown that this mode is more dangerous than the long-wave monotonic instability mode in the entire range of its existence. The instability to the perturbations with nonzero wave numbers is studied numerically by the shooting method. Stability map is obtained. The results confirm the predictions of the longwave analysis. In the second part of the paper, the nonlinear convection regimes are studied by the finite difference method. The calculations give the results consistent with the linear stability analysis. It is found that the primary bifurcation as a result of which the conductive state losses its stability is supercritical. The transformations of the convective flow structure with the change in the Rayleigh–Darcy number are accompanied by the hysteresis phenomena.
Recent advances in bioinspired vision sensor arrays based on advanced optoelectronic materials
Authors: Li Hao , Yu Huiwen , Wu Di , Sun Xidi , Pan Lijia
Published: August 2023

Animals can learn about the outside world in many ways, and the visual organ is a key organ for acquiring information about the outside world. With the continuous development of intelligent technology, artificial vision techniques are becoming easier and more automated; however, the rigidity, process complexity, and complicated optical components of traditional commercial photodetectors have hindered their development in bionic vision. In recent years, a new generation of optoelectronic materials has attracted extensive research due to their simple preparation process, continuously tunable bandgap, and excellent optoelectronic properties. Two-dimensional optoelectronic materials and perovskites have become the most promising and effective optoelectronic materials for next-generation optoelectronic devices. Based on the excellent properties of next-generation optoelectronic materials, they have also triggered intensive exploration by researchers in the field of visual bionics. This paper highlights a review of the latest research progress of next-generation optoelectronic materials, including their preparation methods, working mechanisms, structural designs, and advances in the field of imaging. The applications of new generation optoelectronic materials in visual bionics by simulating biological visual structures are also described. Finally, the prospects and challenges for the development of next-generation optoelectronic materials in the emerging field of bionic vision are discussed.
Photoluminescence imaging of field-installed photovoltaic modules in diffuse irradiance
Authors: Vuković M. , Hillestad M. , Jakovljević M. , S. Flø A. , Olsen E. , Burud I.
Published: August 2023

Photoluminescence imaging under sunlight excitation has in the recent years been proposed as a promising inspection technique of field-installed photovoltaic modules. Virtually, all studies have been conducted in full sunlight and clear sky conditions. A study in which photoluminescence images had been acquired at an irradiance level below 100 W m−2 using the lock-in technique has shown the potential of these images with respect to defect analysis. Additionally, as on-site measurement techniques are subject to weather conditions, it would be favorable to extend the applicability of photoluminescence imaging to a wider range of irradiance levels. A method for photoluminescence imaging which does not use the lock-in technique for the purpose of filtering of sunlight was proposed recently. The present study extends the application of this approach to diffuse irradiance conditions. We demonstrate that the method gives valuable information about the modules also in the case of image acquisition under diffuse global in-plane irradiance as low as 40 W m−2. Photoluminescence images acquired under low irradiance are comparable to electroluminescence images acquired at 10% of short-circuit current. Photoluminescence imaging has also been conducted successfully from the rear of bifacial modules in these illumination conditions.
Phase change-driven photoacoustic oscillations induced by periodic irradiation
Authors: Blanc Nathan , Ramon Guy Z.
Published: August 2023

The photo-acoustic effect is a well-documented phenomenon in which the periodic irradiation of an absorbing media produces an acoustic wave, modulated by thermal expansion. However, little is known about the effect imparted by phase change on this mode of energy conversion, nor has it been considered as a potential method of power production. Herein, we report high-amplitude photo-acoustic oscillations, of up to 145 dB, induced upon irradiation of a water film on the wall of an acoustic loop resonator. While the driving power is quite low (∼4 W), the photo-acoustic oscillations are shown to be significantly amplified by the introduction of phase change in the acoustic cycle. A reduced-order model is formulated and is able to recover key characteristics of the acoustic oscillations, in reasonable agreement with experimental results, and confirms the underlying mechanism of pressure modulation by the phase change. The results presented here can potentially pave the way to improved, solar-driven acoustic energy conversion devices.
Large table-like magnetocaloric effect in boron-doped Er5Si3B0.5 compound
Authors: Tian Lu , Mo Zhaojun , Gong Jianjian , Gao Xinqing , Liu Guodong , Shen Jun
Published: August 2023

In this work, Er5Si3B0.5 compound with the Mn5Si3-type hexagonal structure was synthesized, and the structure, magnetic properties, and the magnetocaloric effect were investigated theoretically and experimentally. The magnetic measurement results show a complex successive magnetic transition below TN. However, the magnetization of the Er5Si3B0.5 compound below TN is saturated under lower magnetic field relative to the Er5Si3 compound. Theoretical calculation indicates that this was attributed to the enhanced inter-orbital exchange interaction after doping B element. The complicated successive magnetic transitions contribute to the table-like magnetocaloric effect observed in the Er5Si3B0.5 compound with a wide temperature region. The maximum magnetic entropy change and the temperature averaged entropy change (30) are 10.1 and 9.02 J/kg K for the Er5Si3B0.5 compound under varying magnetic fields from 0 to 5 T, respectively. The temperature averaged entropy change (30) is reduced by just 11% compared to the maximum magnetic entropy change. While presenting an ideal magnetic refrigeration material with a large table-like magnetocaloric effect for hydrogen liquefaction, our work also demonstrates the feasibility of regulating magnetic behavior through enhanced orbital exchange interactions to develop magnetic refrigeration materials with outstanding performance.
Investigation of strong isothermal stratification effects on multi-mode compressible Rayleigh–Taylor instability
Authors: Aslangil Denis , Wong Man Long
Published: August 2023

Rayleigh–Taylor instability, RTI, occurs at the interface separating two fluids subjected to acceleration when the density gradient and the acceleration are in opposite directions. Previous scientific research primarily considered RTI under the incompressible assumption, which may not be valid in many high-energy-density engineering applications and astrophysical phenomena. In this study, the compressibility effects of the background isothermal stratification strength on multi-mode two-dimensional RTI are explored using fully compressible multi-species direct numerical simulations. Cases under three different isothermal Mach numbers – Ma=0.15,  0.3,  and  0.45 – are investigated to explore weakly, moderately, and strongly stratified compressible RTI, respectively, at an Atwood number of 0.04. Unlike incompressible RTI, an increase in the flow compressibility through the strength of the background stratification can suppress the RTI growth and can lead to a termination of the RTI mixing layer growth with a highly molecularly mixed state. Our findings suggest that even at the chosen relatively low Atwood number, the variable-density effects can be significantly enhanced due to an increase in the background stratification for the compressible RTI as different spatial profiles become noticeably asymmetric across the mixing layer for the strongly stratified case. In addition, this study compares the chaotic behavior of the cases by studying the transport of the turbulent kinetic energy as well as the vortex dynamics. The Reynolds number dependence of the results is also examined with three different Reynolds numbers, and the findings for the large-scale mixing and flow quantities of interest are shown to be universal in the range of the Reynolds numbers studied.
Direct evidence on the crossover from BCC to FCC stability: A lattice-based aggregation-volume-bias Monte Carlo approach to polymorphism
Authors: Chen Bin
Published: August 2023

A lattice-based version of the aggregation-volume-bias Monte Carlo method that was introduced recently has allowed for the extension of the calculation of the nucleation free energies from liquid clusters to solid clusters. Here, it was used to calculate the nucleation free energies of both bcc and fcc clusters formed by Lennard–Jones particles. Under the simulation conditions considered in this study, a cross-over of the thermodynamic stability from the bcc to the fcc structure was observed directly from the free energy results. In addition, the free energies obtained for both types of clusters were used to extrapolate bulk phase information, including chemical potential and surface tension, which revealed that bcc clusters are favored due to the lower surface tension. These results corroborate a recent classical density functional theory study. This work also demonstrates that this approach can be used to predict the entire thermodynamic landscape (i.e., free energies for clusters of different structures and sizes, including an infinitely large cluster, which is the bulk phase), which is important to answer fundamental questions related to crystallization such as the origin of polymorphism.
Eating behaviour, body image, and mental health: updated estimates of adolescent health, well-being, and positive functioning in Aotearoa New Zealand
Authors: Babbott Katie M. , Consedine Nathan S. , Roberts Marion
Published: August 2023

Introduction Body image dissatisfaction and its associated challenges have been related to poorer health outcomes among adolescents worldwide, including disordered eating behaviour, depression, and anxiety. However, current prevalence estimates of these issues in Aotearoa New Zealand or, relatedly, the estimates of positive attitudes and behaviours, such as intuitive eating and body appreciation are dated. Aim The primary aim of this paper was to provide updated estimates for a variety of constructs related to eating behaviours and body image, sourced from a diverse range of early adolescent participants. Methods For this report, a brief online survey was advertised to adolescents throughout Aotearoa New Zealand (n = 893) via school and community noticeboards. Results Approximately one-in-three male participants and one-in-two female participants reported body image dissatisfaction. One in four participants reported clinically significant symptoms of depression and anxiety. Discussion Given such issues, there is clearly still much progress to be made in advancing positive health among early adolescents. Identifying potentially protective constructs such as intuitive eating and body appreciation may offer guidance into the best targets for prevention and early intervention.
TRPML3/BK complex promotes autophagy and bacterial clearance by providing a positive feedback regulation of mTOR via PI3P
Authors: Xu Mengnan , Zhong Xi Zoë , Huang Peng , Jaślan Dawid , Wang Pingping , Sun Xue , Weiden Eva-Maria , EL Hiani Yassine , Grimm Christian , Dong Xian-Ping
Published: August 2023

TRPML3 is a Ca
2+
/Na
+
release channel residing in both phagophores and endolysosomal membranes. It is activated by PI3P and PI3,5P2. Its activity can be enhanced by high luminal pH and by replacing luminal Na
+
with K
+
. Here, we report that big-conductance Ca
2+
-activated potassium (BK) channels form a positive feedback loop with TRPML3. Ca
2+
release via TRPML3 activates BK, which in turn facilitates TRPML3-mediated Ca
2+
release, potentially through removing luminal Na
+
inhibition. We further show that TRPML3/BK and mammalian target of rapamycin (mTOR) form another positive feedback loop to facilitate autophagy induction in response to nutrient starvation, i.e., mTOR inhibition upon nutrient starvation activates TRPML3/BK, and this further reduces mTOR activity, thereby increasing autophagy induction. Mechanistically, the feedback regulation between TRPML3/BK and mTOR is mediated by PI3P, an endogenous TRPML3 activator that is enriched in phagophores and is up-regulated by mTOR reduction. Importantly, bacterial infection activates TRPML3 in a BK-dependent manner, and both TRPML3 and BK are required for mTOR suppression and autophagy induction responding to bacterial infection. Suppressing either TRPML3 or BK helps bacteria survival whereas increasing either TRPML3 or BK favors bacterial clearance. Considering that TRPML3/BK is inhibited by low luminal pH but activated by high luminal pH and PI3P in phagophores, we suggest that TRPML3/BK and mTOR form a positive feedback loop via PI3P to ensure efficient autophagy induction in response to nutrient deprivation and bacterial infection. Our study reveals a role of TRPML3–BK coupling in controlling cellular homeostasis and intracellular bacterial clearance via regulating mTOR signaling.
Stress-dependent activation entropy in thermally activated cross-slip of dislocations
Authors: Wang Yifan , Cai Wei
Published: August 2023

Cross-slip of screw dislocations in crystalline solids is a stress-driven thermally activated process essential to many phenomena during plastic deformation, including dislocation pattern formation, strain hardening, and dynamic recovery. Molecular dynamics (MD) simulation has played an important role in determining the microscopic mechanisms of cross-slip. However, due to its limited timescale, MD can only predict cross-slip rates in high-stress or high-temperature conditions. The transition state theory can predict the cross-slip rate over a broad range of stress and temperature conditions, but its predictions have been found to be several orders of magnitude too low in comparison to MD results. This discrepancy can be expressed as an anomalously large activation entropy whose physical origin remains unclear. Here, we resolve this discrepancy by showing that the large activation entropy results from anharmonic effects, including thermal softening, thermal expansion, and soft vibrational modes of the dislocation. We expect these anharmonic effects to be significant in a wide range of stress-driven thermally activated processes in solids.
Kv12 channels flick the switch
Authors: Short Ben
Published: August 2023

JGP study (Hermanstyne et al. 2023. J. Gen. Physiol.https://doi.org/10.1085/jgp.202213310) shows that Kv12-encoded K+ currents reduce the repetitive firing rates of SCN neurons at night, thereby regulating daily oscillations in the master circadian pacemaker.
Stabilising transient ferromagnetic states in nanopatterned FeRh with shape-induced anisotropy
Authors: Grimes M , Sazgari V , Parchenko S , Zhou J , Soh Y , Heyderman L J , Thomson T , Scagnoli V
Published: August 2023

It is well-known that FeRh undergoes an antiferromagnetic to ferromagnetic (FM) phase transition where the high temperature phase is a low coercivity FM material. However, little is known about the effect of lateral confinement on the transition dynamics in FeRh thin films. Here, we pattern FeRh thin films into arrays of nanowires with a large aspect ratio (100:1) and, with ultrafast probing of the magnetic state in an applied magnetic field, we determine the influence of demagnetization fields on the stability of laser induced FM domains. In particular, with pump-probe Kerr measurements, we demonstrate that, when a magnetic field is applied along the nanowire length, the nanowire arrays exhibit an FM phase (>3.0ns) that is longer-lived than that observed for continuous thin films (≈2.0 ns). With electrical measurements, we also show that the transition temperature depends on the relative orientation of the magnetic field. Indeed, when the FeRh film is patterned with sub-μm features, the transition temperature decreases by up to 7 K depending on the field direction at applied magnetic fields of 1 T. The effects of sample heating are explored using finite-element simulations to determine the heat dissipation following laser excitation across a range of FeRh nanowire widths. These simulations confirm that the increased lifetimes of the magnetic-field-aligned FM domains in the nanowire arrays are not due to differences in heat dissipation. This suggests that FM domain growth and relaxation through the ultrafast phase transition in FeRh nanowires is strongly dependent on the shape anisotropy. This knowledge is important for the fine control of the phase transition in patterned FeRh thin films for nanoscale devices.
Low temperature charge transport study of MWCNT/PEDOT:PSS composites: insulating to metallic regime
Authors: Sharma Meenu , Bhatia Ravi , Sameera I
Published: August 2023

Multiwall carbon nanotube (MWCNT)/poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) composites have been examined for their temperature and magnetic field dependent conductivity behavior. The conductivity ratio, σ
r (σ
300 K/
σ
2 K), is significantly impacted by the sulfuric acid post-treatment of the composites and a slight alteration in MWCNTs loading. By adjusting the loading of MWCNTs in the composites, the charge transport is tuned from insulating to metallic regime. For the low loading of MWCNTs (0.04 wt%), charge transport of the composite lies in the insulating regime and follows a variable range hopping model. At moderate loading of MWCNTs, the transport of the composites lies in the critical regime and the temperature dependent conductivity follows a power law model. As the MWCNTs loading increases to 4 wt%, transport of the composites shifts to the metallic regime with σ
r ∼ 2.8. The temperature dependent conductivity has been explained by using electron-electron interactions and weak localization effects and the conductivity follows ∼T
1/2 and ∼T
3/4 dependence in different temperature regimes. Wave function shrinkage and forward interference effects have been used to evaluate the magnetoconductance (MC) of the samples located in the insulating regime. For the composites lying in the metallic regime, a dominant contribution from weak localization explains the behaviour of the MC. However, for those in the critical regime a combined effect of weak localization and electron-electron interactions has been observed.
Three-dimensional critical points and flow patterns in pulmonary alveoli with rhythmic wall motion
Authors: Dong Jun , Lv Huimin , Yang Yue , Cao Yong , Zhu Yonggang
Published: August 2023

The dynamics of airflow in the pulmonary acini are of broad interest in understanding respiratory diseases and the fate of inhaled particles. This study investigates the three-dimensional (3d) alveolar flows with rhythmic cavity wall motion, using a finite element method based computational fluid dynamics. This study reports the new research findings on the critical points and associated flow patterns. The locations of critical points are found based on the Brouwer degree theory and Broyden’s method. The phase portrait is used to evaluate the flow patterns around the critical points and the stability (repelling/attracting property) of the critical points on the symmetry plane of the alveolus. Based on the Poincare–Bendixson theorem, the closed orbits on the symmetry plane are found which have the capability to alter the spiral direction of the spiral streamlines. In the 3d space, the alveolar flow is symmetric about the geometric symmetry plane of the alveolus. Different types of 3d critical points, including saddle, spiral, and spiral saddle, are revealed. There are only one saddle point and at least one spiral point or spiral saddle in the alveolar flow. Spiral points and spiral saddles are located on the vortex core line and their number is dependent on the Reynolds number and varies with time. The study of critical points and their evolution helps us to understand the mechanism of irreversible transport of particle tracers from a new perspective.
Orientation, electronic decoupling and band dispersion of heptacene on modified and nanopatterned copper surfaces
Authors: Boné Thomas , Windischbacher Andreas , Scheucher Lukas , Presel Francesco , Schnabl Paul , Wagner Marie S , Bettinger Holger F , Peisert Heiko , Chassé Thomas , Puschnig Peter , Ramsey Michael G , Sterrer Martin , Koller Georg
Published: August 2023

The adsorption of heptacene (7 A) on Cu(110) and Cu(110)-(2 × 1)-O was studied with scanning tunneling microscopy, photoemission orbital tomography and density functional calculations to reveal the influence of surface passivation on the molecular geometry and electronic states. We found that the charge transfer into the 7 A molecules on Cu(110) is completely suppressed for the oxygen-modified Cu surface. The molecules are aligned along the Cu-O rows and uncharged. They are tilted due to the geometry enforced by the substrate and the ability to maximize intermolecular π-π overlap, which leads to strong π-band dispersion. The HOMO-LUMO gap of these decoupled molecules is significantly larger than that reported on weakly interacting metal surfaces. Finally, the Cu-O stripe phase was used as a template for nanostructured molecular growth and to assess possible confinement effects.
Realization of black phosphorus-like PbSe monolayer on Au(111) via epitaxial growth
Authors: Wang Jing , Bagheri Tagani Meysam , Zhang Li , Xia Yu , Wu Qilong , Li Bo , Tian Yuan , Yin Long-Jing , Zhang Lijie , Qin Zhihui
Published: August 2023

Lead selenide (PbSe) has been attracted a lot attention in fundamental research and industrial applications due to its excellent infrared optical and thermoelectric properties, toward reaching the two-dimensional limit. Herein, we realize the black phosphorus-like PbSe (α-phase PbSe) monolayer on Au(111) via epitaxial growth, where a characteristic rectangular superlattice of 5 Å × 9 Å corresponding to 1 × 2 reconstruction with respect to the pristine of α-phase PbSe is observed by scanning tunneling microscopy. Corresponding density functional theory calculation confirmed the reconstruction and revealed the driven mechanism, the coupling between monolayer PbSe and Au(111) substrate. The metallic feature of differential conductance spectra as well as the transition of the density of states from semiconductor to metal further verified such coupling. As the unique anisotropic structure, our study provides a pathway towards the synthesis of BP-PbSe monolayer. In addition, it builds up an ideal platform for studying fundamental physics and also excellent prospects in PbSe-based device applications.