80 research outputs found
The giant planet orbiting the cataclysmic binary DP Leonis
Planets orbiting post-common envelope binaries provide fundamental
information on planet formation and evolution, especially for the yet nearly
unexplored class of circumbinary planets. We searched for such planets in \odp,
an eclipsing short-period binary, which shows long-term eclipse-time
variations. Using published, reanalysed, and new mid-eclipse times of the white
dwarf in DP\,Leo, obtained between 1979 and 2010, we find agreement with the
light-travel-time effect produced by a third body in an elliptical orbit. In
particular, the measured binary period in 2009/2010 and the implied radial
velocity coincide with the values predicted for the motion of the binary and
the third body around the common center of mass. The orbital period, semi-major
axis, and eccentricity of the third body are P_c = 28.0 +/- 2.0 yrs, a_c = 8.2
+/- 0.4 AU, and e_c = 0.39 +/- 0.13. Its mass of M_c sin(i_c) = 6.1 +/- 0.5 M_J
qualifies it as a giant planet. It formed either as a first generation object
in a protoplanetary disk around the original binary or as a second generation
object in a disk formed in the common envelope shed by the progenitor of the
white dwarf. Even a third generation origin in matter lost from the present
accreting binary can not be entirely excluded. We searched for, but found no
evidence for a fourth body.Comment: Accepted by A&
Strong CH+ J=1-0 emission and absorption in DR21
We report the first detection of the ground-state rotational transition of
the methylidyne cation CH+ towards the massive star-forming region DR21 with
the HIFI instrument onboard the Herschel satellite. The line profile exhibits a
broad emission line, in addition to two deep and broad absorption features
associated with the DR21 molecular ridge and foreground gas. These observations
allow us to determine a CH+ J=1-0 line frequency of 835137 +/- 3 MHz, in good
agreement with a recent experimental determination. We estimate the CH+ column
density to be a few 1e13 cm^-2 in the gas seen in emission, and > 1e14 cm^-2 in
the components responsible for the absorption, which is indicative of a high
line of sight average abundance [CH+]/[H] > 1.2x10^-8. We show that the CH+
column densities agree well with the predictions of state-of-the-art C-shock
models in dense UV-illuminated gas for the emission line, and with those of
turbulent dissipation models in diffuse gas for the absorption lines.Comment: Accepted for publication in A&
Long-term maintenance of in vitro cultures affects growth and secondary metabolism of St. John's Wort
Dayside thermal structure of Venus' upper atmosphere characterized by a global model
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94843/1/jgre3057.pd
Digital Gene Expression Profiling by 5′-End Sequencing of cDNAs during Reprogramming in the Moss Physcomitrella patens
Stem cells self-renew and repeatedly produce differentiated cells during development and growth. The differentiated cells can be converted into stem cells in some metazoans and land plants with appropriate treatments. After leaves of the moss Physcomitrella patens are excised, leaf cells reenter the cell cycle and commence tip growth, which is characteristic of stem cells called chloronema apical cells. To understand the underlying molecular mechanisms, a digital gene expression profiling method using mRNA 5′-end tags (5′-DGE) was established. The 5′-DGE method produced reproducible data with a dynamic range of four orders that correlated well with qRT-PCR measurements. After the excision of leaves, the expression levels of 11% of the transcripts changed significantly within 6 h. Genes involved in stress responses and proteolysis were induced and those involved in metabolism, including photosynthesis, were reduced. The later processes of reprogramming involved photosynthesis recovery and higher macromolecule biosynthesis, including of RNA and proteins. Auxin and cytokinin signaling pathways, which are activated during stem cell formation via callus in flowering plants, are also activated during reprogramming in P. patens, although no exogenous phytohormone is applied in the moss system, suggesting that an intrinsic phytohormone regulatory system may be used in the moss
ERF105 is a transcription factor gene of Arabidopsis thaliana required for freezing tolerance and cold acclimation
Characterisation of the ERF102 to ERF105 genes of Arabidopsis thaliana and their role in the response to cold stress
The four phylogenetically closely related ERF102 to ERF105 transcription factors of Arabidopsis thaliana are regulated by different stresses and are involved in the response to cold stress
Photoperiod Stress in Arabidopsis thaliana Induces a Transcriptional Response Resembling That of Pathogen Infection
Plants are exposed to regular diurnal rhythms of light and dark. Changes in the photoperiod by the prolongation of the light period cause photoperiod stress in short day-adapted Arabidopsis thaliana. Here, we report on the transcriptional response to photoperiod stress of wild-type A. thaliana and photoperiod stress-sensitive cytokinin signaling and clock mutants and identify a core set of photoperiod stress-responsive genes. Photoperiod stress caused altered expression of numerous reactive oxygen species (ROS)-related genes. Photoperiod stress-sensitive mutants displayed similar, but stronger transcriptomic changes than wild-type plants. The alterations showed a strong overlap with those occurring in response to ozone stress, pathogen attack and flagellin peptide (flg22)-induced PAMP triggered immunity (PTI), which have in common the induction of an apoplastic oxidative burst. Interestingly, photoperiod stress triggers transcriptional changes in jasmonic acid (JA) and salicylic acid (SA) biosynthesis and signaling and results in increased JA, SA and camalexin levels. These responses are typically observed after pathogen infections. Consequently, photoperiod stress increased the resistance of Arabidopsis plants to a subsequent infection by Pseudomonas syringae pv. tomato DC3000. In summary, we show that photoperiod stress causes transcriptional reprogramming resembling plant pathogen defense responses and induces systemic acquired resistance (SAR) in the absence of a pathogen
- …