The switch from mitosis to meiosis is one of the most pivotal events in eukaryotes undergoing sexual reproduction. However, the mechanisms orchestrating meiosis initiation remain elusive, particularly in plants. Flowering plants are heterosporous, with male and female spore genesis adopting different developmental courses. We show here that plant pollen mother cells contain a specific meiosis initiation machinery through characterization of a rice (Oryza sativa) gene, MICROSPORELESS1 (MIL1). The mil1 mutant does not produce microspores in anthers but has the normal female fertility. Detailed molecular and cytological investigations demonstrate that mil1 anthers are defective in the meiotic entry of sporogenous cell progenies and in the differentiation of surrounding somatic cell layers, resulting in locules filled with somatic cells instead of microspores. Furthermore, analysis of mil1 msp1 double mutants reveals that due to the absence of MIL1, the cells in their anther locule center do not activate meiotic cell cycle either, generating a similar anther phenotype to mil1. MIL1 encodes a plant-specific CC-type glutaredoxin, which could interact with TGA transcription factors. These results suggest meiotic entry in microsporocytes is directed by an anther-specific mechanism, which requires MIL1 activity, and redox regulation might play important roles in this process.
Particle inertial focusing in a curved channel promises a big potential for lab-on-a-chip applications. This focusing concept is usually based on the balance of inertial lift force and the drag of secondary flow. This paper proposes a new focusing concept independent of inertial lift force, relying solely on secondary flow drag and particle centrifugal force. Firstly, a focusing mechanism in a serpentine channel is introduced, and some design considerations are described in order to make the proposed focusing concept valid. Then, numerical modelling based on the proposed focusing mechanism is conducted, and the numerical results agree well with the experimental ones, which verify the rationality of proposed mechanism. Thirdly, the effects of flow condition and particle size on the focusing performance are studied. The effect of particle centrifugal force on particle focusing in a serpentine microchannel is carefully evaluated. Finally, the speed of focussed particles at the outlet is measured by a micro-PIV, which further certifies the focusing positions of particles within the cross section. Our study provides insights into the role of centrifugal force on inertial focusing. This paper demonstrates for the first time that a single focusing streak can be achieved in a symmetric serpentine channel. The simple serpentine microchannel can easily be implemented in a single-layer microfluidic device. No sheath flow or external force field is needed allowing a simple operation in a more complex lab-on-a-chip system.
A comprehensive study was performed on hydrogen adsorption and storage in Ca-coated boron fullerenes and nanotubes by means of density functional computations. Ca strongly binds to boron fullerene and nanotube surfaces due to charge transfer between Ca and the B substrate. Accordingly, Ca atoms do not cluster on the surface of the boron substrate, while transition metals (such as Ti and Sc) persist in clustering on the B(80) surface. B(80) fullerene coated with 12 Ca atoms can store up to 60 H(2) molecules with a binding energy of 0.12-0.40 eV/H(2), corresponding to a gravimetric density of 8.2 wt %, while the hydrogen storage capacity in a (9,0) B nanotube is 7.6 wt % with a binding energy of 0.10-0.30 eV/H(2). The Ca-coated boron fullerenes and nanotubes proposed in this work are favorable for reversible adsorption and desorption of hydrogen at ambient conditions.
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