741 research outputs found
Aus baltischer Geistesarbeit : Reden und Aufsätze. Bd.2, H.7
http://tartu.ester.ee/record=b1318718~S1*es
Intumescences On Poplar Leaves. I. Structure And Development
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141211/1/ajb208869.pd
Erinnerte Macht. Antike Herrschergräber in transkultureller Perspektive
Zu den Leitformen der alten Reiche Ostasiens und der westlichen Antike gehören exponierte Gräber der führenden Persönlichkeiten. Die Beiträge untersuchen, wie die Grabanlagen die Erinnerung an den Toten formten, zugleich die Wertvorstellungen ihrer Zeit spiegeln und zur Stabilisierung der geltenden Ordnung beitrugen. Dabei interessiert die Funktion der Gräber als Mittel der Selbstdarstellung und als Selbstbeschreibung des Herrschers. Aufschluss geben vor allem jene Monumente, die vom Regenten selber zu Lebzeiten geplant und errichtet worden sind. Ein zweiter Aspekt ist die Bedeutung des Grabs als Manifestation von Vorstellungen über Herrschaft. So kann die Wahl der Bauform den Bezug auf frühere Denkmäler herstellen und damit den Verstorbenen in eine bestimmte Tradition stellen oder aber grundlegende neue Formen finden und so seine besondere Position betonen. Ebenso untersucht wird der Einfluss der Gräber auf das Bild der Nachwelt von der Person des Herrschers und ihre Instrumentalisierung durch die Nachfolger zur Stabilisierung der eigenen Macht
S-33 constraints on the seawater sulfate contribution in modern seafloor hydrothermal vent sulfides
Author Posting. © Elsevier B.V., 2006. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Geochimica et Cosmochimica Acta 71 (2007): 1170-1182, doi:10.1016/j.gca.2006.11.017.Sulfide sulfur in mid-oceanic ridge hydrothermal vents is derived from leaching of basaltic-sulfide and seawater-derived sulfate that is reduced during high temperature water rock
interaction. Conventional sulfur isotope studies, however, are inconclusive about the mass-balance
between the two sources because 34S/32S ratios of vent fluid H2S and chimney sulfide
minerals may reflect not only the mixing ratio but also isotope exchange between sulfate and
sulfide. Here, we show that high-precision analysis of S-33 can provide a unique constraint
because isotope mixing and isotope exchange result in different Δ33S (≡ δ33S – 0.515 δ34S) values
of up to 0.04 ‰ even if δ34S values are identical. Detection of such small Δ33S differences is
technically feasible by using the SF6 dual-inlet mass-spectrometry protocol that has been
improved to achieve a precision as good as 0.006 ‰ (2σ).
Sulfide minerals (marcasite, pyrite, chalcopyrite, and sphalerite) and vent H2S collected
from four active seafloor hydrothermal vent sites, East Pacific Rise (EPR) 9-10° N, 13° N, and
21° S and Mid-Atlantic Ridge (MAR) 37° N yield Δ33S values ranging from –0.002 to 0.033 and
δ34S from –0.5 to 5.3 ‰. The combined δ34S and Δ33S systematics reveal that 73 to 89 % of vent
sulfides are derived from leaching from basaltic sulfide and only 11 to 27 % from seawater-derived
sulfate. Pyrite from EPR 13° N and marcasite from MAR 37° N are in isotope
disequilibrium not only in δ34S but also in Δ33S with respect to associated sphalerite and
chalcopyrite, suggesting non-equilibrium sulfur isotope exchange between seawater sulfate and
sulfide during pyrite precipitation. Seafloor hydrothermal vent sulfides are characterized by low
Δ33S values compared with biogenic sulfides, suggesting little or no contribution of sulfide from
microbial sulfate reduction into hydrothermal sulfides at sediment-free mid-oceanic ridge
systems. We conclude that 33S is an effective new tracer for interplay among seawater, oceanic
crust and microbes in subseafloor hydrothermal sulfur cycles.S. Ono thanks the Agouron Institute for financial support and funding from the NASA Astrobiology Institute and Carnegie Institution
of Washington for supporting the analytical costs. Funding for O. Rouxel is from the Deep Ocean Exploration Institute at WHOI
Diversity and distribution of subseafloor Thermococcales populations in diffuse hydrothermal vents at an active deep-sea volcano in the northeast Pacific Ocean
Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 111 (2006): G04016, doi:10.1029/2005JG000097.The presence, diversity, and distribution of a key group of subseafloor archaea, the
Thermococcales, was examined in multiple diffuse flow hydrothermal vents at Axial Seamount, an active deep-sea volcano located in the northeast Pacific Ocean. A polymerase chain reaction (PCR) approach was used to determine if this group of subseafloor indicator organisms showed any phylogenetic distribution that may indicate distinct subseafloor communities at vents with
different physical and chemical characteristics. Targeted primers for the Thermococcales 16S rRNA (small subunit ribosomal RNA) gene and intergenic transcribed spacer (ITS) region were
designed and applied to organisms filtered in-situ directly from a variety of diffuse flow vents.
Thermococcales were amplified from 9 of 11 samples examined, and it was determined that the ITS region is a better phylogenetic marker than the 16S rRNA in defining consistent groups of closely related sequences. Results show a relationship between environmental clone distribution
and source vent chemistry. The most highly diluted vents with elevated iron and alkalinity contained a distinct group of Thermococcales as defined by the ITS region, suggesting separate subseafloor Thermococcales populations at diffuse vents within the Axial caldera.This work was supported by Washington Sea
Grant (NA76RG0119), National Science Foundation (OCE 9816491), NSF IGERT (DGE-
9870713), NASA Astrobiology Institute through the Carnegie Geophysical Institute, the
NOAA/PMEL Vents Program, NOAA West Coast and Polar Undersea Research Center, and by the Joint Institute for the Study of the Atmosphere and Ocean under NOAA Cooperative Agreement No. NA117RJ1232
Measurement of the Relative Branching Fraction of to Charged and Neutral B-Meson Pairs
We analyze 9.7 x 10^6 B\bar{B}$ pairs recorded with the CLEO detector to
determine the production ratio of charged to neutral B-meson pairs produced at
the Y(4S) resonance. We measure the rates for B^0 -> J/psi K^{(*)0} and B^+ ->
J/psi K^{(*)+} decays and use the world-average B-meson lifetime ratio to
extract the relative widths f+-/f00 = Gamma(Y(4S) -> B+B-)/Gamma(Y(4S) ->
B0\bar{B0}) = = 1.04 +/- 0.07(stat) +/- 0.04(syst). With the assumption that
f+- + f00 = 1, we obtain f00 = 0.49 +/- 0.02(stat) +/- 0.01(syst) and f+- =
0.51 +/- 0.02(stat) +/- 0.01(syst). This production ratio and its uncertainty
apply to all exclusive B-meson branching fractions measured at the Y(4S)
resonance.Comment: 11 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
Study of the Decays B0 --> D(*)+D(*)-
The decays B0 --> D*+D*-, B0 --> D*+D- and B0 --> D+D- are studied in 9.7
million Y(4S) --> BBbar decays accumulated with the CLEO detector. We determine
Br(B0 --> D*+D*-) = (9.9+4.2-3.3+-1.2)e-4 and limit Br(B0 --> D*+D-) < 6.3e-4
and Br(B0 --> D+D-) < 9.4e-4 at 90% confidence level (CL). We also perform the
first angular analysis of the B0 --> D*+D*- decay and determine that the
CP-even fraction of the final state is greater than 0.11 at 90% CL. Future
measurements of the time dependence of these decays may be useful for the
investigation of CP violation in neutral B meson decays.Comment: 21 pages, 5 figures, submitted to Phys. Rev.
A Search for
We report results of a search for in a sample of 9.7 million
charged meson decays. The search uses both and
decay modes of the , and demands exclusive reconstruction of the
companion decay to suppress background. We set an upper limit on the
branching fraction at 90%
confidence level. With slight modification to the analysis we also establish
at 90% confidence
level.Comment: 10 ages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
First Observation of the Decays and B^{0}\to D^{*-}p\bar{n}$
We report the first observation of exclusive decays of the type B to D^* N
anti-N X, where N is a nucleon. Using a sample of 9.7 times 10^{6} B-Bbar pairs
collected with the CLEO detector operating at the Cornell Electron Storage
Ring, we measure the branching fractions B(B^0 \to D^{*-} proton antiproton
\pi^+) = ({6.5}^{+1.3}_{-1.2} +- 1.0) \times 10^{-4} and B(B^0 \to D^{*-}
proton antineutron) = ({14.5}^{+3.4}_{-3.0} +- 2.7) times 10^{-4}. Antineutrons
are identified by their annihilation in the CsI electromagnetic calorimeter.Comment: 9 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
The influence of ultramafic rocks on microbial communities at the Logatchev Hydrothermal field, located 15°N on the Mid-Atlantic Ridge
The ultramafic-hosted Logatchev hydrothermal field (LHF) on the Mid-Atlantic Ridge is characterized by high hydrogen and methane contents in the subseafloor, which support a specialized microbial community of phylogenetically diverse, hydrogen-oxidizing chemolithoautotrophs. We compared the prokaryotic communities of three sites located in the LHF and encountered a predominance of archaeal sequences affiliated with methanogenic Methanococcales at all three. However, the bacterial composition varied in accordance with differences in fluid chemistry between the three sites investigated. An increase in hydrogen seemed to coincide with the diversification of hydrogen-oxidizing bacteria. This might indicate that the host rock indirectly selects this specific group of bacteria. However, next to hydrogen availability further factors are evident (e.g. mixing of hot reduced hydrothermal fluids with cold oxygenated seawater), which have a significant impact on the distribution of microorganism
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