Magnetic levitation stabilized by streaming fluid flows

We demonstrate that the ubiquitous laboratory magnetic stirrer provides a simple passive method of magnetic levitation, in which the so-called “flea” levitates indefinitely. We study the onset of levitation and quantify the flea’s motion (a combination of vertical oscillation, spinning and “waggling”), finding excellent agreement with a mechanical analytical model. The waggling motion drives recirculating flow, producing a centripetal reaction force that stabilized the flea. Our findings have implications for the locomotion of artificial swimmers and the development of bidirectional microfluidic pumps, and they provide an alternative to sophisticated commercial levitators

Microgravity simulation by diamagnetic levitation: effects of a strong gradient magnetic field on the transcriptional profile of Drosophila melanogaster

<p>Abstract</p> <p>Background</p> <p>Many biological systems respond to the presence or absence of gravity. Since experiments performed in space are expensive and can only be undertaken infrequently, Earth-based simulation techniques are used to investigate the biological response to weightlessness. A high gradient magnetic field can be used to levitate a biological organism so that its net weight is zero.</p> <p>Results</p> <p>We have used a superconducting magnet to assess the effect of diamagnetic levitation on the fruit fly <it>D. melanogaster </it>in levitation experiments that proceeded for up to 22 consecutive days. We have compared the results with those of similar experiments performed in another paradigm for microgravity simulation, the Random Positioning Machine (RPM). We observed a delay in the development of the fruit flies from embryo to adult. Microarray analysis indicated changes in overall gene expression of imagoes that developed from larvae under diamagnetic levitation, and also under simulated hypergravity conditions. Significant changes were observed in the expression of immune-, stress-, and temperature-response genes. For example, several heat shock proteins were affected. We also found that a strong magnetic field, of 16.5 Tesla, had a significant effect on the expression of these genes, independent of the effects associated with magnetically-induced levitation and hypergravity.</p> <p>Conclusions</p> <p>Diamagnetic levitation can be used to simulate an altered effective gravity environment in which gene expression is tuned differentially in diverse <it>Drosophila melanogaster </it>populations including those of different age and gender. Exposure to the magnetic field <it>per se </it>induced similar, but weaker, changes in gene expression.</p

Tapping culture collections for fungal endophytes: first genome assemblies for three genera and five species in the Ascomycota

The Ascomycota form the largest phylum in the fungal kingdom and show a wide diversity of lifestyles, some involving associations with plants. Genomic data are available for many ascomycetes that are pathogenic to plants, but endophytes, which are asymptomatic inhabitants of plants, are relatively understudied. Here, using short- and long-read technologies, we have sequenced and assembled genomes for 15 endophytic ascomycete strains from CABI’s culture collections. We used phylogenetic analysis to refine the classification of taxa, which revealed that 7 of our 15 genome assemblies are the first for the genus and/or species. We also demonstrated that cytometric genome size estimates can act as a valuable metric for assessing assembly “completeness”, which can easily be overestimated when using BUSCOs alone and has broader implications for genome assembly initiatives. In producing these new genome resources, we emphasise the value of mining existing culture collections to produce data that can help to address major research questions relating to plant–fungal interactions

Mechanical vibrations of pendant liquid droplets

A simple optical deflection technique was used to monitor the vibrations of microlitre pendant droplets of deuterium oxide, formamide, and 1,1,2,2-tetrabromoethane. Droplets of different volumes of each liquid were suspended from the end of a microlitre pipette and vibrated using a small puff of nitrogen gas. A laser was passed through the droplets and the scattered light was collected using a photodiode. Vibration of the droplets resulted in the motion of the scattered beam and time-dependent intensity variations were recorded using the photodiode. These time- dependent variations were Fourier transformed and the frequencies and widths of the mechanical droplet resonances were extracted. A simple model of vibrations in pendant/sessile drops was used to relate these parameters to the surface tension, density and viscosity of the liquid droplets. The surface tension values obtained from this method were found to be in good agreement with results obtained using the standard pendant drop technique. Damping of capillary waves on pendant drops was shown to be similar to that observed for deep liquid baths and the kinematic viscosities obtained were in agreement with literature values for all three liquids studied

Monte Carlo study on anomalous carrier diffusion in inhomogeneous semiconductors

We perform ensemble Monte Carlo simulations of electron diffusion in high mobility inhomogeneous InAs layers. Electrons move ballistically for short times while moving diffusively for sufficiently long times. We find that electrons show anomalous diffusion in the intermediate time domain. Our study suggests that electrons in inhomogeneous InAs could be used to experimentally explore generalized random walk phenomena, which, some studies assert, also occur naturally in the motion of animal foraging paths

The behavioural-driven response of the Drosophila imago transcriptome to different types of modified gravity

Genome-wide transcriptional profiling experiments on the International Space Station (ISS) have revealed important alterations in the gene expression of Drosophila. In contrast, simulated microgravity experiments in Earth-based laboratories, where the particular constraints and conditions in orbiting spacecraft are absent, show weaker changes in gene expression. Here we use the "gene expression dynamics inspector" (GEDI) self-organizing maps to investigate the effect of altered gravity on different populations of Drosophila. We employ diamagnetic levitation and different mechanical techniques to generate microgravity and hypergravity and compare the changes in gene expression in these modified environments. In addition to behavioural and reproductive responses detected at the gene expression level, our results also indicate a subtle response of the transcriptome that is finely-tuned to Earth´s gravity