9,479 research outputs found
How micropatterns and air pressure affect splashing on surfaces
We experimentally investigate the splashing mechanism of a millimeter-sized
ethanol drop impinging on a structured solid surface, comprised of
micro-pillars, through side-view and top-view high speed imaging. By increasing
the impact velocity we can tune the impact outcome from a gentle deposition to
a violent splash, at which tiny droplets are emitted as the liquid sheet
spreads laterally. We measure the splashing threshold for different
micropatterns and find that the arrangement of the pillars significantly
affects the splashing outcome. In particular, directional splashing in
direction in which air flow through pattern is possible. Our top-view
observations of impact dynamics reveal that an trapped air is responsible for
the splashing. Indeed by lowering the pressure of the surrounding air we show
that we can suppress the splashing in the explored parameter regime.Comment: 7 pages, 9 figure
Efficient cloning system for construction of gene silencing vectors in Aspergillus niger
An approach based on Gateway recombination technology to efficiently construct silencing vectors was developed for use in the biotechnologically important fungus Aspergillus niger. The transcription activator of xylanolytic and cellulolytic genes XlnR of A. niger was chosen as target for gene silencing. Silencing was based on the expression vector pXLNRir that was constructed and used in co-transformation. From all the strains isolated (N = 77), nine showed poor xylan-degrading activities in two semi-quantitative plate assays testing different activities for xylan degradation. Upon induction on D-xylose, transcript levels of xlnR were decreased in the xlnR-silenced strains, compared to a wild-type background. Under these conditions, the transcript levels of xyrA and xynB (two genes regulated by XlnR) were also decreased for these xlnR-silenced strains. These results indicate that the newly developed system for rapid generation of silencing vectors is an effective tool for A. niger, and this can be used to generate strains with a tailored spectrum of enzyme activities or product formation by silencing specific genes encoding, e.g., regulators such as Xln
- β¦