No abstract

No abstract

No abstract

No abstract

Enhancement of upconversion luminescence is imperative for the applications of upconversion nanocrystals (UCNs). In this work, we investigated the upconversion luminescence enhancement of NaYF4:Yb/Er by Mo(3+) ion doping. It was found that the upconversion luminescence intensities of the green and red emissions of UCNs co-doped with 10 mol% Mo(3+) ions were enhanced by 6 and 8 times, respectively. This enhancement offers a potential increase in the overall detectability of upconversion nanocrystals. HeLa cell imaging using NaYF4:Yb/Er/Mo as luminescent probes showed bright upconversion fluorescence. Moreover, the Mo(3+) doping endowed the UCNs with excellent paramagnetic behavior. It is expected that the as-prepared UCNs with a high upconversion luminescence and excellent paramagnetic properties could be promising bi-functional nanoprobes for sensitive multi-modal bioimaging and other optical applications.

No abstract

One major hindrance that alloy design for additive manufacturing (AM) faces nowadays is hot tearing. Contrary to the previous works which either try to reduce solidification range or introduce grain refinement, the current work presents a new approach of employing segregation engineering to alter the residual stress states at the interdendritic and grain boundary regions and consequently prevent hot tearing. Here, in situ Al alloying is introduced into an existing hot-cracking susceptible highentropy alloy CoCrFeNi. It is found that within a certain range of compositions, such as Al0.5CoCrFeNi, the hot crack density was drastically decreased. During the solidification of this specific alloy composition, Al is firstly ejected from the primary dendritic face-centred cubic (FCC) phase and segregates into the interdendritic regions. Spinodal decomposition then occurs in these Al-enriched regions to form the ordered B2 NiAl and disordered body-centred cubic (BCC) Cr phases. Due to the higher molar volume and lower homologous temperatures of these B2/BCC phases, the inherent residual strain is accommodated and transformed from a maximum 0.006 tensile strain in CoCrFeNi to a compressive strain of ~0.001 in Al0.5CoCrFeNi. It is believed that this grain boundary segregation engineering method could provide a new pathway to systematically counteract the hot tearing problem in additive manufacturing of metals and alloys, using available thermodynamic and kinetic database information.

The analysis of the relationship between regional resources and environment and human activities plays an important role in sustainable regional development. This study proposes the pressure-capacity-governance (PCG) model, an analytic framework for the assessment of the resources and environmental pressure (REP), carrying capacity (RECC) and governance (REG) levels over a large watershed scale, with the Yangtze River Economic Belt (YREB) as the study area. A limiting factor analysis is used to recognize the limiting factors of the regional RECC. The coupling analysis of resources and environmental pressure-capacity-governance identifies the regional potential and utilization direction. The research results are as follows. (1) The REP, RECC and REG levels of the YREB exhibit spatial differences. The REPs of the upper reaches are lower than those of the lower reaches, which does not match the RECC but matches the REG levels.(2) The proportions of unused land, water resources, and atmospheric environmental quality are the main limiting factors of the regional RECC. (3) The PCG analysis framework is used as the basis to divide the YREB into several subareas to analyse the resources and environmental potential carrying capacity and utilization direction of different types of region. This research may provide decision-making references for regional sustainable development at the large watershed scale.