Light-activated ferroelectric transition in layer dependent Bi2O2Se films

Bi2O2Se has attracted intensive attention due to its potential in electronics, optoelectronics, as well as ferroelectric applications. Despite that, there have only been a handful of experimental studies based on ultrafast spectroscopy to elucidate the carrier dynamics in Bi2O2Se thin films, Different groups have reported various ultrafast timescales and associated mechanisms across films of different thicknesses. A comprehensive understanding in relation to thickness and fluence is still lacking. In this work, we have systematically explored the thickness-dependent Raman spectroscopy and ultrafast carrier dynamics in chemical vapor deposition (CVD)-grown Bi2O2Se thin films on mica substrate with thicknesses varying from 22.44 nm down to 4.62 nm at both low and high pump fluence regions. Combining the thickness dependence and fluence dependence of the slow decay time, we demonstrate a ferroelectric transition in the thinner (< 8 nm) Bi2O2Se films, influenced by substrate-induced compressive strain and non-equilibrium states. Moreover, this transition can be manifested under highly non-equilibrium states. Our results deepen the understanding of the interplay between the ferroelectric phase and semiconducting characteristics of Bi2O2Se thin films, providing a new route to manipulate the ferroelectric transition

The next detectors for gravitational wave astronomy

This paper focuses on the next detectors for gravitational wave astronomy which will be required after the current ground based detectors have completed their initial observations, and probably achieved the first direct detection of gravitational waves. The next detectors will need to have greater sensitivity, while also enabling the world array of detectors to have improved angular resolution to allow localisation of signal sources. Sect. 1 of this paper begins by reviewing proposals for the next ground based detectors, and presents an analysis of the sensitivity of an 8 km armlength detector, which is proposed as a safe and cost-effective means to attain a 4-fold improvement in sensitivity. The scientific benefits of creating a pair of such detectors in China and Australia is emphasised. Sect. 2 of this paper discusses the high performance suspension systems for test masses that will be an essential component for future detectors, while sect. 3 discusses solutions to the problem of Newtonian noise which arise from fluctuations in gravity gradient forces acting on test masses. Such gravitational perturbations cannot be shielded, and set limits to low frequency sensitivity unless measured and suppressed. Sects. 4 and 5 address critical operational technologies that will be ongoing issues in future detectors. Sect. 4 addresses the design of thermal compensation systems needed in all high optical power interferometers operating at room temperature. Parametric instability control is addressed in sect. 5. Only recently proven to occur in Advanced LIGO, parametric instability phenomenon brings both risks and opportunities for future detectors. The path to future enhancements of detectors will come from quantum measurement technologies. Sect. 6 focuses on the use of optomechanical devices for obtaining enhanced sensitivity, while sect. 7 reviews a range of quantum measurement options

Ultrasonic Impact Strengthening of Titanium Alloys: State-of-the-art and Prospectives

This review started with the introduction to the principles and research progresses of the ultrasonic impact strengthening technology for titanium alloys. The influences of the properties of titanium alloys were investigated, which was associated with the different parameters of ultrasonic impact strengthening processes(static pressure, ultrasonic amplitude and numbers of rolling). Results show that the optimization of different processing parameters has a significant improvement on the performance strengthening of the titanium alloys. However, there is a critical value of the different processing parameters. Once the critical values arc exceeded, continuing to increase the parameter values will reduce the service performance of the titanium alloys. Finally, the difficulties of ultrasonic impact strengthening technology which used in the engineering applications were summarized. Combined with the development of intelligent manufacturing, the future development of ultrasonic impact strengthening technology was prospected

Preparation of l-Arginine Schiff Bases Modified Chitosan Derivatives and Their Antimicrobial and Antioxidant Properties

We successfully prepared a series of l-arginine Schiff bases acylated chitosan derivatives, aiming to improve the antioxidant activity and antimicrobial activity of chitosan by introducing a furan ring, pyridine ring, and l-arginine structure. The accuracy of the structures of ten compounds was characterized by FT-IR and H-1 NMR. In terms of DPPH radical scavenging activity, except for compound CR3PCA, the scavenging rate of other compounds was higher than chitosan, especially CRCF and CRBF had strong scavenging abilities. At the same time, in the superoxide-radical scavenging activity assay, CRCF, CRBF, CR3PCA, CR2C3PCA, and CR2B3PCA were comparable to positive control at 1.60 mg/mL. Simultaneously, CRFF, CRCF, and CRBF had a certain inhibitory effect on Botrytis cinerea. Furthermore, the inhibitory effect of CRFF, CRCF, and CR3PCA on Staphylococcus aureus was very well, close to the positive control at 1.00 mg/mL. CRCF and CR2B3PCA showed better inhibitory effects on Escherichia coli than other compounds. The MTT assay was used to determine the cytotoxicity of the chitosan derivatives, which proved their safety to fibroblast cells. In summary, the study indicated that some of these compounds have the potential for further development and utilization in the preparation of antioxidants and antimicrobial agents

Interpretable machine learning reveals microbiome signatures strongly associated with dairy cow milk urea nitrogen

Summary: The gut microbiome plays an important role in the healthy and efficient farming of dairy cows. However, high-dimensional microbial information is difficult to interpret in a simplified manner. We collected fecal samples from 161 cows and performed 16S amplicon sequencing. We developed an interpretable machine learning framework to classify individuals based on their milk urea nitrogen (MUN) concentrations. In this framework, we address the challenge of handling high-dimensional microbial data imbalances and identify 9 microorganisms strongly correlated with MUN. We introduce the Shapley Additive Explanations (SHAP) method to provide insights into the machine learning predictions. The results of the study showed that the performance of the machine learning model improved (accuracy = 72.7%) after feature selection on high-dimensional data. Among the 9 microorganisms, g__Firmicutes_unclassified had the greatest impact in the model. This study provides a reference for precision animal husbandry

An Experimental Study on the Physical and Mechanical Properties of Granite after High-Temperature Treatment Considering Anisotropy

The deep burial disposal of nuclear waste and dry hot rock mining relates to the effects of high temperatures on the physical and mechanical properties of granite. Previous studies have shown that due to the anisotropy of mineral arrangements during granite formation, the physical and mechanical properties of granite vary greatly with different temperatures. We conducted wave velocity tests, optical mirror tests, and uniaxial and conventional triaxial compression tests on granite in three orthogonal directions before and after high-temperature treatment. The main innovative conclusions are as follows: (1) High temperatures can cause the density of thermal cracks in the cross-section of granite, which varies with different sampling directions. Temperatures below 400 °C increase the anisotropy of granite, and there are obvious advantages in the development direction. (2) Under the same temperature conditions, granite samples taken parallel to the dominant direction of cracks exhibit the best mechanical properties. (3) In uniaxial compression tests, granite samples after high-temperature treatment are mostly subjected to tensile splitting failure. When the heating temperature is higher than 400 °C, a large number of transgranular cracks are generated during the thermal damage of granite at this temperature stage. Rock samples taken perpendicular to the dominant direction of the crack can generate radial cracks near the main failure surface, while rock samples taken parallel to the dominant direction of the crack can generate more axial cracks

Coupling mechanisms of static and dynamic loads during the ultrasonic impact strengthening of Ti-6Al-4V

The ultrasonic impact-strengthening technology was used to effectively improve the fatigue resistance of the key components, which could be attributed to the association of static and dynamic impact loads. It is widely used in the high-performance manufacturing of critical aerospace components, such as titanium alloys. During the ultrasonic impact-strengthening process, the static and dynamic loading can provide two different deformation mechanisms, which may cause differences in the strengthening effect of the titanium alloys. This study developed an ultrasonic impact-strengthening test platform to investigate the influence mechanisms of static loads and cyclic dynamic impact loads in the ultrasonic impact-strengthening process. Meanwhile, the experiment platform was based on displacement control and could apply either static loads or cyclic dynamic impact loads individually on the surface of the Ti-6Al-4V. The force values in the static load experiments, cyclic dynamic impact experiments, and ultrasonic impact strengthening experiments were analyzed. The results show that the force value in the ultrasonic impact strengthening process is not only the superposition of the static load and the cyclic dynamic impact load, but indicating a coupling effect. The force of ultrasonic impact strengthening process increased by more than 55% compared to the sum of the static load and the maximum dynamic impact load. Moreover, the deformation strain rate of Ti-6Al-4V under separate cyclic dynamic impact loading was simulated. During the ultrasonic impact strengthening process, the deformation strain rate of Ti-6Al-4V could reach 960 s−1, 1587 s−1, and 2043 s−1 when the cyclic impact depths of 5 μm, 10 μm, and 15 μm, respectively. At the same time, the material surface hardening mechanism under the high strain rate cyclic impact loading was analyzed. The hardness of Ti-6Al-4V after the ultrasonic impact-strengthening process increased by more than 11% compared to the original hardness. At last, the strengthening performance of Ti-6Al-4V after the ultrasonic impact strengthening was evaluated. The strengthening mechanisms of static and dynamic loads during the ultrasonic impact strengthening of Ti-6Al-4V was investigated

Effects of Microwave Sintering on Properties and Microstructure of Ferromanganese Alloy Powders

Microwave sintering process was employed to agglomerate ferromanganese alloy powders. The effects of sintering temperature, holding time and particle size composition on the properties and microstructure of sintering products were investigated. The results was shown that increasing sintering temperature or holding time appropriately is beneficial to increase the compressive strength and volume density. SEM and EDAX analysis shows that the liquid phase formed below the melting point in the sintering process, which leads to densification. XRD patterns indicate that the main reaction during microwave sintering is the decarbonization and carburization of iron carbide phase. The experiment demonstrate that the optimum microwave sintering process condition is 1150°C, 10 min and 50% content of the powders with the size of –75 μm