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From 5.5 months of dual-band optical photometric monitoring at the 1 mmag level, BRITE-Constellation has revealed two simultaneous types of variability in the O4I(n)fp star ζ Puppis: one single periodic non-sinusoidal component superimposed on a stochastic component. The monoperiodic component is the 1.78-d signal previously detected by Coriolis/Solar Mass Ejection Imager, but this time along with a prominent first harmonic. The shape of this signal changes over time, a behaviour that is incompatible with stellar oscillations but consistent with rotational modulation arising from evolving bright surface inhomogeneities. By means of a constrained non-linear light-curve inversion algorithm, we mapped the locations of the bright surface spots and traced their evolution. Our simultaneous ground-based multisite spectroscopic monitoring of the star unveiled cyclical modulation of its He ii λ4686 wind emission line with the 1.78-d rotation period, showing signatures of corotating interaction regions that turn out to be driven by the bright photospheric spots observed by BRITE. Traces of wind clumps are also observed in the He ii λ4686 line and are correlated with the amplitudes of the stochastic component of the light variations probed by BRITE at the photosphere, suggesting that the BRITE observations additionally unveiled the photospheric drivers of wind clumps in ζ Pup and that the clumping phenomenon starts at the very base of the wind. The origins of both the bright surface inhomogeneities and the stochastic light variations remain unknown, but a subsurface convective zone might play an important role in the generation of these two types of photospheric variability.
Portal alumni
(2006)
Keine Jobsuche, kein Chef- aber auch kein festes Gehalt. Die Entscheidung fur eine berufliche Selbständigkeit hat sowohl Vor- als auch Nachteile. Welche guten und welche leidvollen Erfahrungen Potsdamer Absolventen mit einer Unternehmensgründung gemacht haben, können Sie in unserem Titelthema der nunmehr vierten Auflage von "portal alumni" lesen. Die Startbedingungen und Motive "unserer" Existenz· gründersind sehr unterschiedlich. So übernahmen manche das elterliche Unternehmen, für einige war die Selbständigkeit die einzige Alternative zur Arbeitslosigkeit. Dass der Schritt nicht immer aus dem Wunsch heraus
gegangen wird, eigene Ideen zu verwirklichen, konstatiert auch Prof Dr. Guido Reger, in seinem Artikel. An der Universität Potsdam erhalten Gründungswillige vielfaltigste Unterstützung. So kommt es also nicht von ungefahr, dass die Hochschule zu den drei Universitäten in Deutschland gehört, die künftigen Selbständigen die besten Bildungsvoraussetzungen bietet, wie kürzlich in einem Ranking ermittelt wurde. Zudem gewann sie in diesem Jahr zum zweiten Mal in Folge beim Businessplanwettbewerb BerlinErandenburg den Hochschulwettbewerb. Außerdem finden Sie in diesem Heft die neue Rubrik "alumni
insight". Lesen Sie dort beispielsweise, warum Stephan Reichelt den Aufstieg auf einen bisher noch nie bezwungenen Berg im Himalaya wagt. Haben auch Sie etwas Ungewöhnliches und Spannendes zu berichten? Haben Sie vielleicht ein Buch geschrieben oder möchten Sie andere Ehemalige zur Eröffnung Ihres Restaurants einladen, dann lassen Sie es uns wissen.
The selaginella genome identifies genetic changes associated with the evolution of vascular plants
(2011)
Vascular plants appeared similar to 410 million years ago, then diverged into several lineages of which only two survive: the euphyllophytes (ferns and seed plants) and the lycophytes. We report here the genome sequence of the lycophyte Selaginella moellendorffii (Selaginella), the first nonseed vascular plant genome reported. By comparing gene content in evolutionarily diverse taxa, we found that the transition from a gametophyte- to a sporophyte-dominated life cycle required far fewer new genes than the transition from a nonseed vascular to a flowering plant, whereas secondary metabolic genes expanded extensively and in parallel in the lycophyte and angiosperm lineages. Selaginella differs in posttranscriptional gene regulation, including small RNA regulation of repetitive elements, an absence of the trans-acting small interfering RNA pathway, and extensive RNA editing of organellar genes.
The water swelling and subsequent solvent exchange including co-nonsolvency behavior of thin films of a doubly thermo-responsive diblock copolymer (DBC) are studied viaspectral reflectance, time-of-flight neutron reflectometry, and Fourier transform infrared spectroscopy.
The DBC consists of a thermo-responsive zwitterionic (poly(4-((3-methacrylamidopropyl) dimethylammonio) butane-1-sulfonate)) (PSBP) block, featuring an upper critical solution temperature transition in aqueous media but being insoluble in acetone, and a nonionic poly(N-isopropylmethacrylamide) (PNIPMAM) block, featuring a lower critical solution temperature transition in water, while being soluble in acetone.
Homogeneous DBC films of 50-100 nm thickness are first swollen in saturated water vapor (H2OorD2O), before they are subjected to a contraction process by exposure to mixed saturated water/acetone vapor (H2OorD2O/acetone-d6 = 9:1 v/v).
The affinity of the DBC film toward H2O is stronger than for D2O, as inferred from the higher film thickness in the swollen state and the higher absorbed water content, thus revealing a pronounced isotope sensitivity.
During the co-solvent-induced switching by mixed water/acetone vapor, a two-step film contraction is observed, which is attributed to the delayed expulsion of water molecules and uptake of acetone molecules.
The swelling kinetics are compared for both mixed vapors (H2O/acetone-d6 and D2O/acetone-d6) and with those of the related homopolymer films.
Moreover, the concomitant variations of the local environment around the hydrophilic groups located in the PSBP and PNIPMAM blocks are followed.
The first contraction step turns out to be dominated by the behavior of the PSBP block, where as the second one is dominated by the PNIPMAM block.
The unusual swelling and contraction behavior of the latter block is attributed to its co-nonsolvency behavior.
Furthermore, we observe cooperative hydration effects in the DBC films, that is, both polymer blocks influence each other's solvation behavior.