552 research outputs found
The structure and energetics of He and He nanodroplets doped with alkaline earth atoms
We present systematic results, based on density functional calculations, for
the structure and energetics of He and He nanodroplets doped with
alkaline earth atoms. We predict that alkaline earth atoms from Mg to Ba go to
the center of He drops, whereas Ca, Sr, and Ba reside in a deep dimple at
the surface of He drops, and Mg is at their center. For Ca and Sr, the
structure of the dimples is shown to be very sensitive to the He-alkaline earth
pair potentials used in the calculations. The transition
of strontium atoms attached to helium nanodroplets of either isotope has been
probed in absorption experiments. The spectra show that strontium is solvated
inside He nanodroplets, supporting the calculations. In the light of our
findings, we emphasize the relevance of the heavier alkaline earth atoms for
analyzing mixed He-He nanodroplets, and in particular, we suggest their
use to experimentally probe the He-He interface.Comment: Typeset using Revtex, 20 pages and 8 Postscript file
Nanosegregation in Na2C60
There is continuous interest in the nature of alkali metal fullerides containing C(4)(60) and C(2)(60),
because these compounds are believed to be nonmagnetic Mott–Jahn–Teller insulators. This idea
could be verified in the case of A(4)C(60), but Na(2)C(60) is more controversial. By comparing the results
of infrared spectroscopy and X-ray diffraction, we found that Na(2)C(60) is segregated into 3-10 nm
large regions. The two main phases of the material are insulating C(60) and metallic Na(3)C(60). We
found by neutron scattering that the diffusion of sodium ions becomes faster on heating. Above
470 K Na(2)C(60) is homogeneous and we show IR spectroscopic evidence of a Jahn–Teller distorted
C(2)(60) anion
Wastewater Treatment in the Diary Industry from Classical Treatment to Promising Technologies: An Overview
Water pollution caused by population growth and human activities is a critical problem exacerbated by limited freshwater resources and increasing water demands. Various sectors contribute to water pollution, with the dairy industry being a significant contributor due to the high concentrations of harmful contaminants in dairy wastewater. Traditional treatment methods have been employed, but they have limitations in terms of effectiveness, cost, and environmental impact. In recent years, membrane separation technology (MST) has emerged as a promising alternative for treating dairy wastewater. Membrane processes offer efficient separation, concentration, and purification of dairy wastewater, with benefits such as reduced process steps, minimal impact on product quality, operational flexibility, and lower energy consumption. However, membrane fouling and concentration polarization present major challenges associated with this technique. Therefore, strategies have been implemented to mitigate these phenomena, including pre-treatment prior to MST, coagulation, and adsorption. Recently, 3D printing technology has gained prominence as one of the latest and most notable advancements for addressing these issues. This comprehensive review examines the drawbacks and benefits of conventional methods employed in dairy wastewater treatment and explores the utilization of membrane technology as an alternative to these approaches. Additionally, the latest technologies implemented to mitigate or alleviate the limitations of membrane technology are discussed
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