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The deposition of high-critical temperature yttrium barium copper oxide thin films on a LaMgAl11O19 substrate material prepared by a pulsed laser ablation method is discussed. The superconductivity of the films and the structure and quality of the substrates were determined by four-probe resistivity and susceptibility measurements and x-ray diffraction. The utility of the new substrate for high frequency applications was demonstrated.

A study was conducted to examine the microscopic film structure and the magnetic hysteresis of Mg[B.sub.2] thin films synthesized by using hybrid physical chemical vapor deposition (HPCVD) which do not show dendritic avalanche compared to those prepared by pulsed laser deposition (PLD). The critical current density ([J.sub.c]), estimated from the magnetic hysteresis based on the Bean's critical-state model which showed a much higher [J.sub.c] in the PLD film than in a HPCVD film indicated higher vortex pinning in the PLD film.

The current-carrying capability of high quality epitaxial Mg[B.sub.2] films prepared by using the hybrid physical-chemical vapor deposition method is studied by using transport measurement in nanobridge constrictions and magnetization measurement. An extremely high self-field critical current density is observed, which has shown an excellent current-carrying capability in these films.

Melt-textured growth method enables the preparation of DyBa2Cu3O4 crystals. Virgin magnetization curves of these crystals exhibit an on-parameters scaling behavior in the temperature range from 10 to 85 K. Temperature influences the irreversibility of magnetization. Extended Bean model explains the scaling behavior of these crystals.

We present a MgB2-based Microwave Kinetic Inductance Detector (MKID) featuring a quality factor Qi ~ 105 and noise equivalent power NEP ~ 10−14  W / Hz at 2 K. In comparison to YBCO-based MKIDs, the MgB2 detector shows greater sensitivity to both temperature and magnetic field, a result of its two-gap nature and relatively low critical H c 2 field. Our data indicate that MgB2 is more advantageous for MKID applications at temperatures lower than 3 K. [ABSTRACT FROM AUTHOR]

Timber–concrete composite structure is a type of efficient combination form composed of concrete floors and timber beams or floors through shear connectors, and shows good application potential in the floor system of timber buildings. The long-term performance of the timber–concrete composite structures is complex and is affected by the creep of timber and concrete, as well as the long-term slip of the shear connectors. This article presents a comprehensive overview of the research status on the long-term behavior of timber–concrete composite members and different shear connectors. For the shear connectors, the effects of loading levels, environments, and component materials on their creep coefficients are summarized. As to the timber–concrete composite members, both the experimental and numerical investigations are gathered into discussions: the connection types, component materials, loading conditions, and durations in the long-term tests are also discussed; various models for describing long-term behavior of timber, concrete, and connection systems are provided, and then a comprehensive description of the progress of numerical investigations over the last decades is made. In addition, the suggestions for future research are proposed to reach a clearer understanding of the bending mechanisms and mechanical characteristics of timber–concrete composite structures. [ABSTRACT FROM AUTHOR]

This study explores the dynamic field of 3D-printed hydrogels, emphasizing advancements and challenges in customization, fabrication, and functionalization for applications in biomedical engineering, soft robotics, and tissue engineering. It delves into the significance of tailored biomedical scaffolds for tissue regeneration, the enhancement in bioinks for realistic tissue replication, and the development of bioinspired actuators. Additionally, this paper addresses fabrication issues in soft robotics, aiming to mimic biological structures through high-resolution, multimaterial printing. In tissue engineering, it highlights efforts to create environments conducive to cell migration and functional tissue development. This research also extends to drug delivery systems, focusing on controlled release and biocompatibility, and examines the integration of hydrogels with electronic components for bioelectronic applications. The interdisciplinary nature of these efforts highlights a commitment to overcoming material limitations and optimizing fabrication techniques to realize the full potential of 3D-printed hydrogels in improving health and well-being. [ABSTRACT FROM AUTHOR]

Multifunctional materials based on carbon xerogel (CX) with embedded bismuth (Bi) and iron (Fe) nanoparticles are tested for ultrasensitive amperometric detection of lead cation (Pb2+) and hydrogen peroxide (H2O2). The prepared CXBiFe-T nanocomposites were annealed at different pyrolysis temperatures (T, between 600 and 1050 °C) and characterized by X-ray diffraction (XRD), Raman spectroscopy, N2 adsorption, dynamic light scattering (DLS), and electron microscopies (SEM/EDX and TEM). Electrochemical impedance spectroscopy (EIS) and square wave anodic stripping voltammetry (SWV) performed at glassy carbon (GC) electrodes modified with chitosan (Chi)-CXBiFe-T evidenced that GC/Chi-CXBiFe-1050 electrodes exhibit excellent analytical behavior for Pb2+ and H2O2 amperometric detection: high sensitivity for Pb2+ (9.2·105 µA/µM) and outstanding limits of detection (97 fM, signal-to-noise ratio 3) for Pb2+, and remarkable for H2O2 (2.51 µM). The notable improvements were found to be favored by the increase in pyrolysis temperature. Multi-scale parameters such as (i) graphitization, densification of carbon support, and oxide nanoparticle reduction and purification were considered key aspects in the correlation between material properties and electrochemical response, followed by other effects such as (ii) average nanoparticle and Voronoi domain dimensions and (iii) average CXBiFe-T aggregate dimension. [ABSTRACT FROM AUTHOR]

The breakdown characteristics are very important for GaN high-electron-mobility transistors (HEMTs), which affect the application voltage, power density, efficiency, etc. In order to further enhance the breakdown voltage of the device, it is necessary to carry out research on the breakdown mechanisms of the device. This article summarizes several breakdown mechanisms of GaN devices, including electric field concentration, buffer leakage current, gate leakage current, and vertical breakdown. In order to suppress the breakdown mechanisms, techniques such as the use of a field plate, reduced surface field (RESURF), back barrier, gate dielectric, substrate removal, and addition of AlGaN channels can be developed. With the continuous development of various technologies, the breakdown characteristics of GaN devices can be fully explored, laying the foundation for improving the performance of power electronic systems. [ABSTRACT FROM AUTHOR]

Examines the microstructural features of the buckminsterfullerene. Use of electron microscopy and electron diffraction; Characterization of the grains of the samples; Influence of high-density cracks on the magnetic and electronic properties of the samples.

Protoplast culture and transformation technology offer a novel method for developing new plant varieties. Nonetheless, the effective preparation of protoplasts and transformation technology specific to celery has yet to be achieved. This study utilized celery seedling leaves as the primary materials to examine the key factors influencing protoplast isolation. The aim was to prepare leaf protoplasts with a high yield and of high quality and subsequently conduct transient gene transformation and expression. The findings indicated that the most effective procedure for isolating and purifying protoplasts was enzymatic digestion using an enzyme solution consisting of 2.0% cellulase, 0.1% pectolase, and 0.6 M mannitol for a duration of 8 h. Subsequently, the protoplasts were filtered through a 400-mesh sieve and purified through centrifugation at 200× g. Within this system, the overall protoplast yield was exceptionally high, reaching a viability rate of up to 95%. The transient transformation system yielded a maximum transformation efficiency of approximately 53%, as evaluated using the green fluorescent protein (GFP) as a reporter gene. The parameters of the transient transformation system were as follows: a protoplast concentration of 5 × 105 cells·mL−1, exogenous DNA concentration of 500 μg·mL−1, final concentration of PEG4000 at 40%, and transformation duration of 15 min. The transient transformation system was also utilized to further analyze the protein localization characteristics of the celery transcription factor AgMYB80. The findings indicated that AgMYB80 predominantly localizes in the nucleus, thereby confirming the reliability and effectiveness of the transient transformation system. This study successfully established an efficient system for isolating, purifying, and transforming celery protoplasts, and will serve as a basis for future studies on molecular biology and gene function. [ABSTRACT FROM AUTHOR]

Two MgB2 samples were prepared using the spark plasma sintering (SPS) technique at different temperatures—950 °C (S1) and 975 °C (S2)—for 2 h under 50 MPa pressure to study the influence of preparation temperature on different facets, namely those perpendicular (PeF) and parallel (PaF) to the compression direction of uniaxial pressure during the SPS of MgB2 samples. We analyzed the superconducting properties of the PeF and PaF of two MgB2 samples prepared at different temperatures from the curves of the critical temperature (TC), the curves of critical current density (JC), the microstructures of MgB2 samples, and the crystal size from SEM. The values of the onset of the critical transition temperature, Tc,onset, were around 37.5 K and the transition widths were about 1 K, which indicates that the two samples exhibit good crystallinity and homogeneity. The PeF of the SPSed samples exhibited slightly higher JC compared with that of the PaF of the SPSed samples over the whole magnetic field. The values of the pinning force related to parameters h0 and Kn of the PeF were lower than those of the PaF, except for Kn of the PeF of S1, which means that the PeF has a stronger GBP than the PaF. In low field, the most outstanding performance was S1-PeF, whose critical current density (JC) was 503 kA/cm2 self-field at 10 K, and its crystal size was the smallest (0.24 µm) among all the tested samples, which is consistent with the theory that a smaller crystal size can improve the JC of MgB2. However, in high field, S2-PeF had the highest JC value, which is related to the pinning mechanism and can be explained by grain boundary pinning (GBP). With an increase in preparation temperature, S2 showed a slightly stronger anisotropy of properties. In addition, with an increase in temperature, point pinning becomes stronger to form effective pinning centers, leading to a higher JC. [ABSTRACT FROM AUTHOR]

Recently, Pei et al. (National Science Review2023, nwad034, 10.1093/nsr/nwad034) reported that ambient pressure β -MoB2 (space group: R 3 ¯ m ) exhibits a phase transition to α -MoB2 (space group: P 6 / m m m ) at pressure P~70 GPa, which is a high-temperature superconductor exhibiting T c = 32   K at P~110 GPa. Although α -MoB2 has the same crystalline structure as ambient-pressure MgB2 and the superconducting critical temperatures of α -MoB2 and MgB2 are very close, the first-principles calculations show that in α -MoB2, the states near the Fermi level, ε F , are dominated by the d-electrons of Mo atoms, while in MgB2, the p-orbitals of boron atomic sheets dominantly contribute to the states near the ε F . Recently, Hire et al. (Phys. Rev. B2022, 106, 174515) reported that the P 6 / m m m -phase can be stabilized at ambient pressure in Nb1−xMoxB2 solid solutions, and that these ternary alloys exhibit T c ~ 8   K . Additionally, Pei et al. (Sci. China-Phys. Mech. Astron. 2022, 65, 287412) showed that compressed WB2 exhibited T c ~ 15   K at P~121 GPa. Here, we aimed to reveal primary differences/similarities in superconducting state in MgB2 and in its recently discovered diboride counterparts, Nb1−xMoxB2 and highly-compressed WB2. By analyzing experimental data reported for P6/mmm-phases of Nb1−xMoxB2 (x = 0.25; 1.0) and highly compressed WB2, we showed that these three phases exhibit d-wave superconductivity. We deduced 2 Δ m (0) k B T c = 4.1 ± 0.2 for α -MoB2, 2 Δ m (0) k B T c = 5.3 ± 0.1 for Nb0.75Mo0.25B2, and 2 Δ m (0) k B T c = 4.9 ± 0.2 for WB2. We also found that Nb0.75Mo0.25B2 exhibited high strength of nonadiabaticity, which was quantified by the ratio of T θ T F = 3.5 , whereas MgB2, α-MoB2, and WB2 exhibited T θ T F ~ 0.3 , which is similar to the T θ T F in pnictides, A15 alloys, Heusler alloys, Laves phase compounds, cuprates, and highly compressed hydrides. [ABSTRACT FROM AUTHOR]

Highly porous carbon black and micro/mesoporous activated carbon were impregnated with cobalt and nickel nitrates, followed by heat treatment at 850 °C in nitrogen. Detailed information about chemistry and porosity was obtained using XPS, XRD, TEM/EDX, and nitrogen adsorption. The samples were used as ORR catalysts. Marked differences in the performance were found depending on the type of carbon. Differences in surface chemistry and porosity affected the chemistry of the deposited metal species that governed the O2 reduction efficiency along with other features of the carbon supports, including electrical conductivity and porosity. While dissociating surface acidic groups promoted the high dispersion of small metal species, carbon reactivity with oxygen and acidity limited the formation of the most catalytically active Co3O4. Formation of Co3O4 on the highly conductive carbon black resulted in an excellent performance with four electrons transferred and a current density higher than that on Pt/C. When Co3O4 was not formed in a sufficient quantity, nickel metal nanoparticles promoted ORR on the Ni/Co-containing samples. The activity was also significantly enhanced by small pores that increased the ORR efficiency by strongly adsorbing oxygen, which led to its bond splitting, followed by the acceptance of four electrons. [ABSTRACT FROM AUTHOR]

Superconducting M g B 2 films are fabricated by a hybrid physical-chemical vapor deposition method on S i 3 N 4 spheres in diameter of 2 mm. Resistance measurement shows that the film transits into the superconducting state at a critical temperature of about 33 K. Diamagnetic properties of the film-coated sphere are tested, in comparison with a YBCO bulk sphere. In both zero field cooling and field cooling conditions, the film-coated sphere behaves exactly like a type-II superconductor in weak field. To understand the diamagnetism of film-coated sphere better, we numerically studied the levitation force decay when there are non-superconducting loopholes on the film. Results show that one single small loophole seems insignificant, but flux line passage created by two or more disconnected loopholes are vital. [ABSTRACT FROM AUTHOR]