A non-stationary polar gap model first proposed by Ruderman & Sutherland (1975) is modified and applied to spark–associated pulsar emission at radio wavelengths. It is argued that under physical and geometrical conditions prevailing above pulsar polar cap, highly non-stationary spark discharges do not occur at random positions. Instead, sparks should tend to operate in well determined preferred...

In rod-shaped bacteria, septal peptidoglycan synthesis involves the late recruitment of the ftsI gene product (PBP3 in Escherichia coli) to the FtsZ ring. We show that in Caulobacter crescentus, PBP3 accumulates at the new pole at the beginning of the cell cycle. Fluorescence recovery after photobleaching experiments reveal that polar PBP3 molecules are, constantly and independently of FtsZ, re...

Male meiosis in Trichosia pubescens (Sciaridae) was investigated by means of serial section electron microscopy and immunofluorescence light microscopy. From earlier studies of another sciarid fly, Sciara coprophila (Phillips (1967) J. Cell. Biol. 33, 73-92), it is known that the spindle poles in sciarid spermatogonia are characterized by pairs of 'giant centrioles', ring-shaped organelles comp...

In Drosophila, polar plasm contains polar granules, which deposit the factors required for the formation of pole cells, germ line progenitors. Polar granules are tightly associated with mitochondria in early embryos, suggesting that mitochondria could contribute to pole cell formation. We have previously reported that mitochondrial large and small rRNAs (mtrRNAs) are transported from mitochondr...

The pole-sitter concept is a solution to the poor temporal resolution of polar observations from highly inclined, low Earth orbits and the poor high latitude coverage from geostationary orbit. It considers a spacecraft that is continuously above either the North or South Pole and, as such, can provide real-time, continuous and hemispheric coverage of the polar regions. Despite the significant d...

Bacterial replication origins move towards opposite ends of the cell during DNA segregation. We have identified a proline-rich polar protein, PopZ, required to anchor the separated Caulobacter crescentus chromosome origins at the cell poles, a function that is essential for maintaining chromosome organization and normal cell division. PopZ interacts directly with the ParB protein bound to speci...

Low energy ion and electron measurements made over the south and north polar regions of the sun by the HISCALE instrument on the Ulysses spacecraft during its solar minimum polar passages are summarized. The polar flux levels were considerably reduced in comparison to fluxes in the vicinity of the heliospheric current sheet. Flux variations with a period of ∼ 26 days were seen to nearly 80◦S bu...

Posterior polar plasm of the Drosophila egg has been shown to function autonomously in germ cell determination after transplantation to either the anterior or mid-ventral region of the early embryo. By means of similar transplantations, we have tested the ability of polar plasm of Drosophila immigrans to induce the formation of pole cells in a Drosophila melanogaster embryo. After the transplan...

During the first three cleavage divisions of the egg nuclei a precise sequence of spindle orientation and elongation parallel to the longitudinal axis of the egg is apparently involved in positioning one nucleus among the polar granules at the posterior pole of the egg. The size of this nucleus, and the position at which the egg cleaves when pole cell formation occurs, appear to constitute part...

www.sciencemag.org SCIENCE VOL 339 18 JANUARY 2013 247 COVER Map of highest surface temperature in the north polar region of Mercury superimposed on topography measured by the MESSENGER spacecraft. Red areas surrounding the pole (center) reach temperatures above 450 K. Blue and purple areas inside polar impact craters never exceed 100 K and are suffi ciently cold to harbor water ice and frozen ...