Stable isotopes in atmospheric water vapour are important tracers for investigating water vapour transport, mixing and phase transition. In recent years, with the rapid development of analytical techniques, research on water vapour stable isotopes has been widely conducted worldwide. In this review, we summarize basic theory and examine various methodologies employed to study stable isotopes in atmospheric water vapour, ranging from traditional collection methods to more recent advancements in laser absorption spectroscopy, satellite remote sensing, and isotope general circulation models(iGCMs). We pointed out the critical role played by isotopes in tracing moisture sources, understanding precipitation patterns, and reconstructing past climates. We identify gaps in knowledge, particularly in the representation of isotopic processes in climate models. Furthermore, we highlighted future research should focus on enhancing isotopic measurement technologies, integrating isotopic data with climatic indicators to improve model accuracy, and expanding isotopic studies to underserved water cycle dynamics. This review aims to provide suggestions for future investigations to deepen our understanding of atmospheric water vapour stable isotopes and their significance in climatology and hydrology.
Spatter during laser powder bed fusion(LPBF)can induce surface defects,impacting the fatigue performance of the fabricated components.Here,we reveal and explain the links between vapour depression shape and spatter dynamics during LPBF of an Al-Fe-Zr aluminium alloy using high-speed synchrotron x-ray imaging.We quantify the number,trajectory angle,velocity,and kinetic energy of the spatter as a function of vapour depression zone/keyhole morphology under industry-relevant processing conditions.The depression zone/keyhole morphology was found to influence the spatter ejection angle in keyhole versus conduction melting modes:(i)the vapour-pressure driven plume in conduction mode with a quasi-semi-circular depression zone leads to backward spatter whereas;and(ii)the keyhole rear wall redirects the gas/vapour flow to cause vertical spatter ejection and rear rim droplet spatter.Increasing the opening of the keyhole or vapour depression zone can reduce entrainment of solid spatter.We discover a spatter-induced cavity mechanism in which small spatter particles are accelerated towards the powder bed after laser-spatter interaction,inducing powder denudation and cavities on the printed surface.By quantifying these laser-spatter interactions,we suggest a printing strategy for minimising defects and improving the surface quality of LPBF parts.
Da GuoRubén Lambert-GarciaSamy HocineXianqiang FanHenry GreenhalghRavi ShahaniMarta MajkutAlexander RackPeter D LeeChu Lun Alex Leung
There are urgent needs of volatile amine gas sensors with high-performance in food quality control,disease monitoring and environmental pollution.Thin-film fluorescent probe is suitable for amine vapour sensing due to its high sensitivity,high selectivity,and no polluting analyte.Herein,a novel fluorescent probe based on indacenodithiophene structure withπconjugated system was designed and synthesized.The experimental results show that the films prepared by this material exhibit rapid and distinct fluorescence quenching after being exposed to saturated vapours of primary amine,secondary amine and tertiary amine represented by n-propylamine,diethylamine and trimethylamine,respectively.The quenching of fluorescence is 84%,87%and 96%,respectively,within 10 s.The detection mechanism of probe for primary amine is based on specific chemical reaction,while the detection mechanism for secondary amine and tertiary amine is intramolecular charge transfer.Further experiments show that the detection limit of the fluorescent probe for trimethylamine,an important marker of food spoilage,could reach 4.610 ppt.On-site detection based on spoilage of small yellow croaker suggests the material possesses the potential for food freshness detection.This simple fluorogenic probe is an original approach to simplify real-time visual monitoring of volatile amine vapour.
