物理最新文献

This study investigates the prompt fission neutron (PFN) multiplicity distribution in the spontaneous fission (SF) of (^{244})Fm. Experimental data were obtained using the complete fusion reaction (^{206})Pb((^{40})Ar,2n)(^{244})Fm, obtaining a mean of (3.6 pm 0.1) emitted neutrons per SF event. The symmetry of the PFN multiplicity distribution suggests no significant influence of additional fission modes, aligning with theoretical predictions that indicate the dominance of the standard fission mode. At the same time, comparison with neighboring isotopes points at a possible additional fission mode in (^{246})Fm.

An analytical study of wave theory-based multilayered SPR-based fiber optic biosensor by shinning Bessel-Gauss (BG) beam is proposed here for early diagnosis of dengue infection. At first, this wave theory-based analytical model shined by Gaussian (G) beam is validated with the already reported experimental data, where the obtained results are in good accord with the experimental findings presented by Y. M. Kamil et al. in 2018. So, it affords the experimental confirmation of the validity of the proposed theory. The enhancement in sensitivity is 1.99 times ascertained by employing G beam for our proposed structure at a spectral sensitivity of 10.008 nm/nM. This theoretical investigation has then been extended utilizing the BG beam, where the observed sensitivity is increased to 59,602.00 dB/RIU and 20.016 nm/nM with a resolution of 1.68 × 10^–7, which is 3.98 times higher than the referred published work. Here, the limit of detection is 0.06 pM with a minimum change in transmitted output power of 0.8658 milliwatt/RIU. When the DENV-II E protein concentration ranges from 0.08 pM to 0.6 nM, higher spectral shifts are observed. Consequently, enhancements in sensitivity and resolution can be achieved at reduced concentrations, paving the idea of diagnosis of dengue infection at an early stage.

La_0.7Ca_0.3MnO₃ (LCMO) is a prominent semi-metallic ferromagnet known for its strong spin polarization and sharp magnetic transition temperature. This makes it a highly attractive candidate for various applications in spintronic technology, memory devices, and multifunctional systems. The structural and physical properties of LCMO can be significantly altered by adjusting the annealing atmosphere during synthesis. Here, we present an in-depth analysis on the influence of oxygen annealing on the structural characteristics, magnetic behavior, and magnetocaloric properties of LCMO compound. The analysis of X-ray diffraction patterns by using Rietveld refinement method revealed that all the samples formed an orthorhombic structure with the Pnma space group with a decrease in cell volume for samples (S2 and S3) annealed in oxygen atmosphere. The samples S1, S2, and S3 undergo ferromagnetic-paramagnetic phase transitions at 247, 263, and 264 K, respectively. This suggests that the oxygenated annealing induce the oxygen homogeneity in the sample. On the other hand, the field-dependent magnetization measurements and Arrott analysis indicated a first-order ferromagnetic phase transition in all the prepared samples. The maximum change in magnetic entropy was evaluated by using numerical approximation of Maxwells thermodynamic relation. It was noted that the maximum change in magnetic entropy shows monotonic behaviour with oxygen annealing. This ability to adjust magnetization and magnetocaloric effect by altering the annealing atmosphere of LCMO presents a novel approach for developing magnetic refrigerants and gaining insight into fundamental phenomena.

This paper presents the results of studying the structural features and physical properties of two-component composites (1-x)PbFe₁₂O₁₉–xPbTiO₃, obtained from pre-synthesized and mechanically activated powders. To control the physical properties of composites, in addition to changing the dopant (PbTiO₃) concentration within the range of 0.2–0.8 in steps of 0.2, the method of mechanical activation (nanostructuring) was used. This method implies that the Bridgman anvils simultaneously apply a compressive force to the powder placed between them and produce a shear deformation by rotating the lower anvil. X-ray diffraction revealed a sharp decrease in the unit cell parameters of the dopant of the initial composition at x = 0.4, followed by a similarly sharp leap in the parameters of the hexagonal cell after mechanical activation. The dimensions of the coherent scattering regions (D) of the PbFe₁₂O₁₉ component after mechanical activation decreased by more than a half, while the dislocation density (ρ_D) and the magnitude of microstrains (ε) increased by more than an order of magnitude. It was found that the magnetic phase transition temperature of composites decreases by about 14 °C with increasing dopant concentration, and the nanostructuring of composites leads to a further decrease in the transition temperature by another 12–36 °C, depending on the dopant concentration. The band gap E_g of the nanostructured compositions increases by approximately 0.3 eV regardless of the dopant concentration. Using the impedance spectroscopy method, it has been discovered that the dependence of the grain capacitance C_g(T) in the temperature range of 150–350 °C has a bell-shaped form, which is explained in terms of Maxwell–Wagner polarization, where the relaxation is of the non-Debye type.

This study aims to elucidate the correlation between the partial spinel oxide phase ratio and the electronic energy configuration of Co(Gaₓ,Al_1-x)₂O₄ (x = 0.00, 0.25, 0.50, 0.75, and 1.00) spinel oxides. Nanoparticles of Co(Ga,Al)₂O₄ were synthesized through a chemical route, and the crystal structure parameters and electronic energy configurations were investigated concerning the positions of Al and Ga in the spinel oxide lattice. Rietveld refinements were conducted based on three different phase formations, including a normal spinel lattice and two separate partial inverse spinel phase formations. The lattice parameters for Co(Ga₀.₅,Al₀.₅)₂O₄ particles, assuming three crystal phases in Rietveld refinement, were calculated as 8.2181 ± 0.0001 Å (in normal spinel oxide phase), 8.22551 ± 0.0001 Å (in partial spinel oxide phase), and 8.1485 ± 0.0001 Å (in partial spinel oxide phase). The parameters were associated with the lattice micro strain of samples. Additionally, a significant change in electronic energy configurations was demonstrated by the trend in band gap values associated with Al replacement in the lattice and cation atom positions. The highest band gap, 3.48 ± 0.01 eV, was calculated for Co(Ga₀.₅,Al₀.₅)₂O₄ particles.

In this study the radiotoxic ²¹⁰Po activity concentrations were measured, in 25 different tobacco samples grown in the Aegean, Eastern Black Sea, Southeastern Anatolia, and Mediterranean regions of Türkiye, using an alpha spectrometer. The measured ²¹⁰Po activity concentrations in tobacco samples determined by radiochemical processes ranged from a minimum of 2.7 ± 0.6 Bq kg⁻¹ to a maximum of 10.8 ± 1.5 Bq kg⁻¹. According to the ²¹⁰Po activity concentrations, the annual effective doses to which adults are internally exposed were calculated to be in the range of 9.5 µSv y⁻¹ to 45.0 µSv y⁻¹, while lung doses were calculated to be in the range of 65.8 µSv y⁻¹ to 312.2 µSv y⁻¹. It has been determined how dangerous the radiotoxic ²¹⁰Po in the tobacco plants is in terms of public health. The concentrations of elements (Al, P, Ni, Pb, Mn, Fe, Cd, Cu, Zn) in tobacco samples were also measured using ICP-OES. These data were compared with results from other similar studies around the world and with UNSCEAR limit values.

Due to the special semiconductor-to-metal transition (SMT) properties, vanadium dioxide (VO₂) film has attracted tremendous interest for both the fundamental correlated electronic structure studies and the phase-change devices applications. It is known that the SMT features of VO₂ are always closely associated with the film preparation, which becomes an important issue for the research in this field. In the current study, we explored the preparation of VO₂/Al₂O₃ films by adopting the sol-gel method in conjunction with a subsequent annealing process. The effects of nitrogen flow rate on the structure, composition, morphology, and electrical properties of the VO₂ films were investigated. Results showed that V₂O₅ film was formed without nitrogen protection. As the nitrogen flow rate increased from 100 mL/min to 500 mL/min, the films exhibited a polycrystalline structure with VO₂ (020) preferred orientation. Simultaneously, the V⁴⁺ content within the film remained largely constant, while the surface grains gradually enlarged, accompanied by a more dispersed grain size distribution. Moreover, the increased nitrogen flow rate led to a consistent reduction in both the transition temperature during the heating process and the hysteresis width of the film. The asymmetry of the hysteresis loop of the thin film was also enhanced, which was closely related to the grain size distribution on the surface of the film. These findings not only elucidated the influence of nitrogen flow rate on the phase transition properties of VO₂ during annealing, but also offered a novel insight into the regulation of VO₂ phase transitions.