4,633 research outputs found
Planetary environment simulation - Martian sand and dust storm simulation and evaluation, volume 2
Particle behavior in simulated Martian sand and dust stor
African vegetable diversity in the limelight: project activities by ProNIVA.
Poster presented at Botanical Congress. Hamburg (Germany), 3-7 Sep 200
Cosmic-ray induced background intercomparison with actively shielded HPGe detectors at underground locations
The main background above 3\,MeV for in-beam nuclear astrophysics studies
with -ray detectors is caused by cosmic-ray induced secondaries. The
two commonly used suppression methods, active and passive shielding, against
this kind of background were formerly considered only as alternatives in
nuclear astrophysics experiments. In this work the study of the effects of
active shielding against cosmic-ray induced events at a medium deep location is
performed. Background spectra were recorded with two actively shielded HPGe
detectors. The experiment was located at 148\,m below the surface of the Earth
in the Reiche Zeche mine in Freiberg, Germany. The results are compared to data
with the same detectors at the Earth's surface, and at depths of 45\,m and
1400\,m, respectively.Comment: Minor errors corrected; final versio
Near Infrared Imaging of the Hubble Deep Field with The Keck Telescope
Two deep K-band () images, with point-source detection limits of
mag (one sigma), taken with the Keck Telescope in subfields of the
Hubble Deep Field, are presented and analyzed. A sample of objects to K=24 mag
is constructed and and colors are measured. By
stacking visually selected objects, mean colors can be measured to
very faint levels; the mean color is constant with apparent
magnitude down to mag.Comment: Replaced with slightly revised source positions and corrected V-I
magnitudes (which were incorrect in the Tables and Figure 5). 18 pages. The
data are publicly available at http://www.cco.caltech.edu/~btsoifer/hdf.html
along with a high-resolution version of Fig.
Microbial âgardeningâ by a seaweed holobiont: Surface metabolites attract protective and deter pathogenic epibacterial settlement
Epimicrobial communities on seaweed surfaces usually contain not only potentially pathogenic but also potentially beneficial microâorganisms. Capacity of terrestrial plants for chemically mediated recruitment, that is, âgardeningâ of bacterial communities in the rhizosphere was recently demonstrated. Empirical evidence directly linking such chemical âgardeningâ with the beneficial role of gardened microbes in terrestrial plants is rare and largely missing for aquatic macrophytes.
Here, we demonstrate that our model invasive seaweed holobiont Agarophyton vermiculophyllum possesses beneficial microbiota on its surface that provide protection from bacterial pathogens. Metabolites from the algal holobiontâs surface reduced settlement of opportunistic pathogens but attracted protective epibacterial settlement.
We tested 58 different bacterial species (isolated from the surface of A. vermiculophyllum ) individually in tip bleaching assays. Kordia algicida was identified as a âsignificant pathogenâ inducing a bleaching disease. In addition, nine other species significantly reduced the risk of algal bleaching and were thus âsignificantly protectiveâ. Additionally, two âpotential pathogensâ and 10 âpotential protectorsâ were identified. When 19 significant and potential protectors and 3 significant and potential pathogens were tested together, the protective strains fully prevented bleaching, suggesting that a component of A. vermiculophyllumâs epimicrobiome provides an associational defence against pathogens. Chemically mediated selective recruitment of microbes was demonstrated in bioassays, where A. vermiculophyllum surface metabolites attracted the settlement of protective strains, but reduced settlement of pathogens.
Synthesis . The capacity of an aquatic macrophyte to chemically âgardenâ protective microâorganisms to the benefit of strengthened disease resistance is demonstrated for the first time. Such a role of surface chemistry in âgardeningâ of microbes as found in the current study could also be applicable to other host plantâmicrobe interactions. Our results may open new avenues towards manipulation of the surface microbiome of seaweeds via chemical âgardening,â enhancing sustainable production of healthy seaweeds
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