| 11. |
- Yao, Lun, et al.
(författare)
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Multiple Gene Repression in Cyanobacteria Using CRISPRi
- 2016
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Ingår i: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 5:3, s. 207-212
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Tidskriftsartikel (refereegranskat)abstract
- We describe the application of clustered regularly interspaced short palindromic repeats interference (CRISPRi) for gene repression in the model cyanobacterium Synechcocystis sp. PCC 6803. The nuclease-deficient Cas9 from the type-II. CRISPR/Cas of Streptrococcus pyogenes was used to repress green fluorescent protein (GFP) to negligible levels. CRISPRi was also used to repress formation of carbon storage compounds polyhydroxybutryate (PHB) and glycogen during nitrogen starvation. As an example of the potential of CRISPRi for basic and applied cyanobacteria research, we simultaneously knocked down 4 putative aldehyde reductases and dehydrogenases at 50-95% repression. This work also demonstrates that tightly repressed promoters allow for inducible and reversible CRISPRi in cyanobacteria.
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| 12. |
- Yao, Lun, et al.
(författare)
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Pooled CRISPRi screening of the cyanobacterium Synechocystis sp PCC 6803 for enhanced industrial phenotypes
- 2020
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Ingår i: Nature Communications. - : Nature Research. - 2041-1723. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Cyanobacteria are model organisms for photosynthesis and are attractive for biotechnology applications. To aid investigation of genotype-phenotype relationships in cyanobacteria, we develop an inducible CRISPRi gene repression library in Synechocystis sp. PCC 6803, where we aim to target all genes for repression. We track the growth of all library members in multiple conditions and estimate gene fitness. The library reveals several clones with increased growth rates, and these have a common upregulation of genes related to cyclic electron flow. We challenge the library with 0.1 M L-lactate and find that repression of peroxiredoxin bcp2 increases growth rate by 49%. Transforming the library into an L-lactate-secreting Synechocystis strain and sorting top lactate producers enriches clones with sgRNAs targeting nutrient assimilation, central carbon metabolism, and cyclic electron flow. In many examples, productivity can be enhanced by repression of essential genes, which are difficult to access by transposon insertion.
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| 13. |
- Zhang, Bo lun, et al.
(författare)
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Experimental study on film cooling performance of a turbine blade tip with a trapezoidal slot cooling scheme in transonic flow using PSP technique
- 2022
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Ingår i: Experimental Thermal and Fluid Science. - : Elsevier BV. - 0894-1777. ; 130
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Forskningsöversikt (refereegranskat)abstract
- A turbine blade tip with a trapezoidal slot cooling scheme is first proposed in the current paper. The film cooling characteristics of a turbine blade tip with a trapezoidal slot scheme are experimentally studied by the pressure sensitive paint (PSP) technique in transonic flow. Varieties of density ratio, tip clearance gap and position of the trapezoidal slot scheme are selected as investigation parameters. The mainstream Reynolds number is 370,000 based on the blade axial chord length. The cascade exit Mach numbers are is 1.05. The results indicate that increasing the density ratio has a positive effect on the film cooling effectiveness of the whole blade tip with a pressure side trapezoidal slot scheme at a small tip clearance gap, whereas it decreases the film cooling effectiveness upstream of the blade tip at the large tip clearance gap. For the blade tip with a pressure side trapezoidal slot scheme, the film cooling effectiveness of the tip clearance gap of 1.5% near the trailing edge is higher than that of the other tip clearance gaps at the same density ratio condition. Changing the trapezoidal slot position from the tip pressure side to the tip midline increases the film cooling effectiveness near the trailing edge.
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| 14. |
- Zhang, Yichen, et al.
(författare)
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Massive Protostars in a Protocluster—A Multi-scale ALMA View of G35.20-0.74N
- 2022
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 936:1
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Tidskriftsartikel (refereegranskat)abstract
- We present a detailed study of the massive star-forming region G35.2-0.74N with Atacama Large Millimeter/submillimeter Array (ALMA) 1.3 mm multi-configuration observations. At 0.″2 (440 au) resolution, the continuum emission reveals several dense cores along a filamentary structure, consistent with previous ALMA 0.85 mm observations. At 0.″03 (66 au) resolution, we detect 22 compact sources, most of which are associated with the filament. Four of the sources are associated with compact centimeter continuum emission, and two of these are associated with H30α recombination line emission. The H30α line kinematics shows the ordered motion of the ionized gas, consistent with disk rotation and/or outflow expansion. We construct models of photoionized regions to simultaneously fit the multiwavelength free-free fluxes and the H30α total fluxes. The derived properties suggest the presence of at least three massive young stars with nascent hypercompact H ii regions. Two of these ionized regions are surrounded by a large rotating structure that feeds two individual disks, revealed by dense gas tracers, such as SO2, H2CO, and CH3OH. In particular, the SO2 emission highlights two spiral structures in one of the disks and probes the faster-rotating inner disks. The 12CO emission from the general region reveals a complex outflow structure, with at least four outflows identified. The remaining 18 compact sources are expected to be associated with lower-mass protostars forming in the vicinity of the massive stars. We find potential evidence for disk disruption due to dynamic interactions in the inner region of this protocluster. The spatial distribution of the sources suggests a smooth overall radial density gradient without subclustering, but with tentative evidence of primordial mass segregation.
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| 15. |
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