| 1. |
- Adyari, Bob, et al.
(författare)
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Strong impact of micropollutants on prokaryotic communities at the horizontal but not vertical scales in a subtropical reservoir, China
- 2020
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 721
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Tidskriftsartikel (refereegranskat)abstract
- Micropollutants have become of great concern, because of their disrupting effects on the structure and function of microbial communities. However, little is known about the relative importance of trace micropollutants on the aquatic prokaryotic communities as compared to the traditional physico-chemical characteristics, especially at different spatial dimensions. Here, we investigated free-living (FL) and particle-associated (PA) prokaryotic communities in a subtropical water reservoir, China, across seasons at horizontal (surface water) and vertical (depth-profile) scales by using 16S rRNA gene amplicon sequencing. Our results showed that the shared variances of physico-chemicals and micropollutants explained majority of the spatial variations in prokaryotic communities, suggesting a strong joint effect of the two abiotic categories on reservoir prokaryotic communities. Micropollutants appeared to exert strong independent influence on the core sub-communities (i.e., abundant and wide-spread taxa) than on the satellite (i.e., less abundant and narrow-range taxa) counterparts. The pure effect of micropollutants on both core and satellite sub-communities from FL and PA fractions was similar to 1.5 folds greater than that of physico-chemical factors at the horizontal scale, whereas an opposite effect was observed at the vertical scale. Moreover, eight micropollutants including anti-fungal agents, antibiotics, bisphenol analogues, stimulant and UV-filter were identified as the major disrupting compounds with strong associations with core taxa of typical freshwater prokaryotes. Altogether, we concluded that the ecological disrupting effects of micropollutants on prokaryotic communities may vary along horizontal and vertical dimensions in freshwater ecosystems.
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| 2. |
- Zhang, Xueyi, et al.
(författare)
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Synthesis of Self-Pillared Zeolite Nanosheets by Repetitive Branching
- 2012
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 336:6089, s. 1684-1687
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Tidskriftsartikel (refereegranskat)abstract
- Hierarchical zeolites are a class of microporous catalysts and adsorbents that also contain mesopores, which allow for fas transport of bulky molecules and thereby enable improved performance in petrochemical and biomass processing. We used repetitive branching during one-step hydrothermal crystal growth to synthesize a new hierarchical zeolite made of orthogonally connected microporous nanosheets. The nanosheets are 2 nanometers thick and contain a network of 0.5-nanometer micropores. The house-of-cards arrangement of the nanosheets creates a permanent network of 2- to 7-nanometer mesopores, which, along with the high external surface area and reduced micropore diffusion length, account for higher reaction rates for bulky molecules relative to those of other mesoporous and conventional MFI zeolites.
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| 3. |
- Zhou, Xin, et al.
(författare)
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3D-imaging of selective laser melting defects in a Co-Cr-Mo alloy by synchrotron radiation micro-CT
- 2015
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Ingår i: Acta Materialia. - : Elsevier BV. - 1359-6454 .- 1873-2453. ; 98, s. 1-16
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Tidskriftsartikel (refereegranskat)abstract
- Microstructure defects set the mechanical property limits for solid Co-Cr-Mo alloy prepared by selective laser melting (SLM). Previous studies were mainly based on 2D SEM images and thus not able to provide information of the 3D morphologies of the complex defects. In this paper, the remaining porosities in Co-Cr-Mo alloy parts prepared by selective laser melting were presented in relation to the laser processing parameters. In order to understand the defect forming mechanism, accurate 3D images of defects inside SLM fabricated Co-Cr-Mo samples were provided by synchrotron radiation micro-CT imaging of 300 pm thick slices cut from a 10 mm cube. With 3D reconstructed images distinctive morphologies of SLM defects spanning across the consolidated powder layers were generated. The faults can be classified as single layer or multi-layers defects. The accidental single layer defects form as gaps between adjacent laser melt tracks or melt track discontinuousness caused by inherent fluid instability under various disturbances. The first formed single layer defect generates often a multi-layer defect spanning for 2-3 subsequent powder layers. By stabilizing the melt pool flow and by reducing the surface roughness through adjusting processing parameters it appears possible to reduce the defect concentrations.
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| 4. |
- Zhou, Xin, et al.
(författare)
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Balling phenomena in selective laser melted tungsten
- 2015
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Ingår i: Journal of Materials Processing Technology. - : Elsevier BV. - 0924-0136 .- 1873-4774. ; 222, s. 33-42
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Tidskriftsartikel (refereegranskat)abstract
- Selective laser melting (SLM) of pure tungsten was carried out and the relevant consolidation issues were investigated. It was observed that balling of melted droplets at the laser focal points and entrapped cavities hindered the preparation of fully dense parts. An analysis of the balling mechanism reveals that SLM of tungsten is a process where melt spreading and solidification compete with each other and the final result is determined by intrinsic tungsten properties and the set laser processing parameters. Melted tungsten droplets wetted its own solid substrate at a low speed driven by capillary force, but solidified simultaneous at a high speed driven by the existing steep temperature gradient. Melted droplets solidified before spreading completely and kept their globular geometry instead of creating a flat layer. Tungsten bodies reaching a density of 14.8-15.2 g/cm(3) were prepared with an open irregular porosity and surface roughness. With a second laser scanning the balling W droplets were remelted at the building surface resulting in a much smoother appearance with less porosity and indicated a way to further improve relative density, near 16 g/cm(3) (82.9% theoretical density). Oxidation must be avoided, as any oxide contamination enriched preferably around the melt pool edge, changing the surface tension gradient and the thermocapillary convection thereby increasing balling.
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| 5. |
- Zhou, Xin, et al.
(författare)
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Textures formed in a CoCrMo alloy by selective laser melting
- 2015
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 631, s. 153-164
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Tidskriftsartikel (refereegranskat)abstract
- Unique crystal textures formed by selective laser melting of a CoCrMo alloy were characterized by electron backscattered diffraction. Preferred crystallographic orientations were found for individual grains in the solid alloy microstructure. Along the building or radial grain growth direction in the rapidly cooling melt pool the formed columnar grains were not purely < 001 > or < 111 >, as reported before, but a concurrence of < 001 > and < 011 >. Along the scanning direction, a (011) < 100 > texture was limited to the outmost surface whereas in the solid bulk the preferred orientation was a < 001 > fiber texture.
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