便携式超声诊断仪的新发展

便携式超声诊断仪是近年来快速发展的新方向,它的出现和推广将改进医疗保健的质量,降低费用,可能给整个医疗事业带来新的变化。     

Portable gamma spectrometry with cerium-doped lanthanum bromide scintillators: Suitability assessments for luminescence and electron spin resonance dating applications

Cerium-doped lanthanum bromide (LaBr₃:Ce) crystals offer a range of improved scintillation properties over traditional NaI:Tl crystals for in situ gamma spectrometry. At present, however, it remains unclear whether the internal radioactivity of LaBr₃:Ce detectors compromises their suitability for low-level activity radioisotope measurements of natural sedimentary deposits, such as those required in luminescence and electron spin resonance (ESR) dating. In this study we investigate the suitability of a commercial LaBr₃:Ce detector for measuring individual concentrations of ⁴⁰K, ²³⁸U and ²³²Th using predefined ‘energy windows’ from gamma ray spectra. Performance tests have been undertaken using reference materials with well-constrained radioisotope concentrations (the Oxford calibration blocks) and compared with results obtained for a NaI:Tl detector of the same geometry. These tests reveal that the LaBr₃:Ce detector has a non-negligible intrinsic activity that needs to be accurately quantified prior to measuring any gamma ray spectra in the field. Compared to the NaI:Tl detector, the energy resolution of the LaBr₃:Ce detector is improved by a factor of two, or more, for the main indicator isotope photopeaks in the ⁴⁰K, ²³⁸U and ²³²Th decay series. Signal-to-noise ratios for the LaBr₃:Ce detector show a 25-35% improvement over those of the NaI:Tl detector. In addition, the LaBr₃:Ce detector is characterised by suitable energy linearity over the full spectral range of interest for the ⁴⁰K, ²³⁸U and ²³²Th decay series. Replicate gamma ray measurements made with the LaBr₃:Ce and NaI:Tl detectors for 20 natural sedimentary samples from the Lower Tejo River basin, Portugal, and the Duero River basin, Spain, yield consistent radioisotope concentrations and gamma dose rate estimates. These results are encouraging and suggest that LaBr₃:Ce detectors can provide suitable estimates of individual radioisotope concentrations in low-level activity (0.5-1.5 Gy/ka) environments, providing that their intrinsic activity is adequately measured and subtracted from field spectra. Our comparison also reveals that subtraction of the intrinsic activity from LaBr₃:Ce spectra produces a significant reduction in the precision with which radionuclide concentrations can be determined using the ‘energy windows’ approach. This shortcoming necessitates longer counting times in natural sedimentary environments and overshadows the practical advantages that LaBr₃:Ce detectors might otherwise offer for luminescence and ESR dating applications.     

Recoverable Flexible Perovskite Solar Cells for Next-Generation Portable Power Sources

Flexible perovskite solar cells (FPSCs) with excellent recoverability show a wide range of potential applications in portable power sources. The recoverability of FPSCs requires outstanding bendability of each functional layer, including the flexible substrates, electrodes, perovskite light absorbers, and charge transport materials. This review highlights the recent progress and practical applications of high-recoverability FPSCs, and illustrates the routes toward improvement of the recoverability and environmental stability through the choice of flexible substrates and the preparation of high-quality perovskite films, as well as the optimization of charge-selective contacts. In addition, we explore the intrinsic properties of each functional layer from the physical perspective and analyze how to select suitable functional layers. Additionally, some effective strategies are summarized, including material modification engineering of selective contacts, additives and interface engineering of interlayers, which can release mechanical stress and increase the power-conversion efficiency (PCE) and recoverability of the FPSCs. The challenges of making high-performance FPSCs with long-term stability and high recoverability are discussed. Finally, future applications and perspectives for FPSCs are discussed, aiming to promote more extensive commercialization processes for lightweight and durable FPSCs.