220 research outputs found
Competitive dynamics of two erosion patterns around a cylinder
We investigate experimentally the local erosion of a granular bed near a
fixed vertical cylinder that emerges from the bed. The onset of erosion arising
at the base of the cylinder and usually ascribed to the wrapping horseshoe
vortex is determined and rationalized by a flow contraction effect. We report a
new erosion pattern visible downstream of the cylinder that consists of two
side-by-side elongated holes. This pattern is observed for flow regimes close
to the horseshoe scour onset, whose growth usually inhibits its spatiotemporal
development.Comment: 6 pages, 6 figure
Experimental investigation of tsunami waves generated by granular collapse into water
The generation of a tsunami wave by an aerial landslide is investigated
through model laboratory experiments. We examine the collapse of an initially
dry column of grains into a shallow water layer and the subsequent generation
of waves. The experiments show that the collective entry of the granular
material into water governs the wave generation process. We observe that the
amplitude of the wave relative to the water height scales linearly with the
Froude number based on the horizontal velocity of the moving granular front
relative to the wave velocity. For all the different parameters considered
here, the aspect ratio and the volume of the column, the diameter and density
of the grains, and the height of the water, the granular collapse acts like a
moving piston displacing the water. We also highlight that the density of the
falling grains has a negligible influence on the wave amplitude, which suggests
that the volume of grains entering the water is the relevant parameter in the
wave generation.Comment: 23 pages, 16 figure
Plasmacytoid dendritic cells migrate in afferent skin lymph (Correction: vol 180, pg 5963, 2008)
Comparative studies of photochemical cross-linking methods for stabilizing the bulk hetero-junction morphology in polymer solar cells
Next-generation plasmids for transgenesis in zebrafish and beyond
Transgenesis is an essential technique for any genetic model. Tol2-based transgenesis paired with Gateway-compatible vector collections has transformed zebrafish transgenesis with an accessible, modular system. Here, we established several next-generation transgenesis tools for zebrafish and other species to expand and enhance transgenic applications. To facilitate gene-regulatory element testing, we generated Gateway middle entry vectors harboring the small mouse beta-globin minimal promoter coupled to several fluorophores, CreERT2, and Gal4. To extend the color spectrum for transgenic applications, we established middle entry vectors encoding the bright, blue-fluorescent protein mCerulean and mApple as an alternative red fluorophore. We present a series of p2A peptide-based 3' vectors with different fluorophores and subcellular localizations to co-label cells expressing proteins of interest. Lastly, we established Tol2 destination vectors carrying the zebrafish exorh promoter driving different fluorophores as a pineal gland-specific transgenesis marker active prior to hatching and through adulthood. exorh-based reporters and transgenesis markers also drive specific pineal gland expression in the eye-less cavefish (Astyanax). Together, our vectors provide versatile reagents for transgenesis applications in zebrafish, cavefish, and other models
Next-generation plasmids for transgenesis in zebrafish and beyond
Transgenesis is an essential technique for any genetic model. Tol2-based transgenesis paired with Gateway-compatible vector collections has transformed zebrafish transgenesis with an accessible, modular system. Here, we established several next-generation transgenesis tools for zebrafish and other species to expand and enhance transgenic applications. To facilitate gene-regulatory element testing, we generated Gateway middle entry vectors harboring the small mouse betaglobin minimal promoter coupled to several fluorophores, CreERT2, and Gal4. To extend the color spectrum for transgenic applications, we established middle entry vectors encoding the bright, blue-fluorescent protein Cerulean and mApple as an alternative red fluorophore. We present a series of p2A peptide-based 3' vectors with different fluorophores and subcellular localizations to co-label cells expressing proteins of interest. Lastly, we established Tol2 destination vectors carrying the zebrafish exorh promoter driving different fluorophores as a pineal gland-specific transgenesis marker active prior to hatching and through adulthood. exorh-based reporters and transgenesis markers also drive specific pineal gland expression in the eye-less cavefish (Astyanax). Together, our vectors provide versatile reagents for transgenesis applications in zebrafish, cavefish, and other models
Toward Improved Lifetimes of Organic Solar Cells under Thermal Stress: Substrate-Dependent Morphological Stability of PCDTBT:PCBM Films and Devices
Morphological stability is a key requirement for outdoor operation of organic solar cells. We demonstrate that morphological stability and lifetime of polymer/fullerene based solar cells under thermal stress depend strongly on the substrate interface on which the active layer is deposited. In particular, we find that the stability of benchmark PCDTBT/PCBM solar cells under modest thermal stress is substantially increased in inverted solar cells employing a ZnO substrate compared to conventional devices employing a PEDOT:PSS substrate. This improved stability is observed to correlate with PCBM nucleation at the 50 nm scale, which is shown to be strongly influenced by different substrate interfaces. Employing this approach, we demonstrate remarkable thermal stability for inverted PCDTBT:PC70BM devices on ZnO substrates, with negligible (<2%) loss of power conversion efficiency over 160 h under 85 °C thermal stress and minimal thermally induced “burn-in” effect. We thus conclude that inverted organic solar cells, in addition to showing improved environmental stability against ambient humidity exposure as widely reported previously, can also demonstrate enhanced morphological stability. As such we show that the choice of suitable substrate interfaces may be a key factor in achieving prolonged lifetimes for organic solar cells under thermal stress conditions
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