We report on field-aligned currents (FAC) obtained from precise magnetic field measurements made onboard the Orsted and Magsat satellites when the interplanetary magnetic field (IMF) was near zero. We found that Region 1/Region 2 currents persist through southward IMF, IMF -• 0, and northward IMF; also the central area of both the northern and southern polar caps is always filled with FACs, eve...

Dynamic instability, polarity, and spatiotemporal organization are hallmarks of the microtubule cytoskeleton that allow formation of complex structures such as the eukaryotic spindle. No similar structure has been identified in prokaryotes. The bacteriophage-encoded tubulin PhuZ is required to position DNA at mid-cell, without which infectivity is compromised. Here, we show that PhuZ filaments,...

Type III secretion (T3S) systems are largely used by pathogenic gram-negative bacteria to inject multiple effectors into eukaryotic cells. Upon cell contact, these bacterial microinjection devices insert two T3S substrates into host cell membranes, forming a so-called 'translocon' that is required for targeting of type III effectors in the cell cytosol. Here, we show that secretion of the trans...

Vibrio alginolyticus normally has a single polar flagellum whose number and placement are regulated positively by FlhF. FlhF is a GTPase and homolog of a signal recognition particle (SRP) protein called Ffh and SRP receptor FtsY. FlhF is located at the cell pole and directs formation of the flagellum. To study the mechanism of FlhF localization, we introduced random mutations into flhF by means...

In this work we find the shape and dimension of the solar wind transition surfaces, namely the slow (sonic), the fast magnetosonic and the Alfvén surface, as a function of heliospheric latitude using actual experimental data from Ulysses spacecraft during its first pole to pole journey. We also give the temporal variation of the radius of these surfaces using measurements from spacecraft at 1 A...

The convergence of columns in the univariate qd-algorithm to reciprocals of polar singularities of meromorphic functions has often proved to be very useful. Any q-column corresponding to a “simple pole of isolated modulus” converges to the reciprocal of the corresponding pole. By performing an equivalence transformation of the underlying corresponding continued fraction and programming the new ...

The entire framework of microtubules (MTs) in the mitotic apparatus of Ochromonas danica is reconstructed (except at the spindle poles) from transverse serial sections. Eleven spindles were sectioned and used for numerical data, but only four were reconstructed: a metaphase, an early anaphase, a late anaphase, and telophase. Four major classes of MTs are observed: (a) free MTs (MTs not attached...

Stochastic processes are thought to mediate localization of membrane-associated chemotaxis signaling clusters in peritrichous bacteria. Here, we identified a new family of ParA-like ATPases (designated ParC [for partitioning chemotaxis]) encoded within chemotaxis operons of many polar-flagellated γ-proteobacteria that actively promote polar localization of chemotaxis proteins. In Vibrio cholera...

Polar-orbiting satellite observations are of fundamental importance to explore the main scientific challenges in Arctic Ocean, as they provide information on bio-geo-physical variables with a denser spatial and temporal coverage than in-situ instruments such harsh inaccessible environment. However, limited by lack near North Pole (Polar gap), polar night, frequent cloud cover or haze over ocean...