Afterpulse Measurements of R7081 Photomultipliers for the Double Chooz Experiment

We present the results of afterpulse measurements performed as qualification test for 473 inner detector photomultipliers of the Double Chooz experiment. The measurements include the determination of a total afterpulse occurrence probability as well as an average time distribution of these pulses. Additionally, more detailed measurements with different light sources and simultaneous charge and timing measurements were performed with a few photomultipliers to allow a more detailed understanding of the effect. The results of all measurements are presented and discussed

The PHENIX Experiment at RHIC

The physics emphases of the PHENIX collaboration and the design and current status of the PHENIX detector are discussed. The plan of the collaboration for making the most effective use of the available luminosity in the first years of RHIC operation is also presented.Comment: 5 pages, 1 figure. Further details of the PHENIX physics program available at http://www.rhic.bnl.gov/phenix

Handbuch zur Benutzung von GRIPS und des Graphiksystems der ZRZ

SIGLECopy held by FIZ Karlsruhe; available from UB/TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische Informationsbibliothek2. rev. ed.DEGerman

Evaluating the multiple-sulfur isotope signature of Eoarchean rocks from the Isua Supracrustal Belt (Southwest-Greenland) by MC-ICP-MS: Volcanic nutrient sources for early life

On the anoxic Archean Earth, prior to the onset of oxidative weathering, electron acceptors were relatively scarce, perhaps limiting microbial productivity. An important metabolite may have been sulfate produced during the photolysis of volcanogenic SO₂ gas. Multiple sulfur isotope data can be used to track this sulfur source, and indeed this record indicates SO₂ photolysis dating back to at least 3.7 Ga, that is, as far back as proposed evidence of life on Earth. However, measurements of multiple sulfur isotopes in some key strata from that time can be challenging due to low sulfur concentrations. Some studies have overcome this challenge with NanoSIMS or optimized gas-source mass spectrometry techniques, but those instruments are not readily accessible. Here, we applied an aqua regia leaching protocol to extract small amounts of sulfur from whole rocks for analyses of multiple sulfur isotopes by multi-collector inductively coupled plasma mass spectrometry (MC-ICP- MS). Measurements of standards and replicates demonstrate good precision and accuracy. We applied this technique to meta-sedimentary rocks with putative biosignatures from the Eoarchean Isua Supracrustal Belt (ISB, >3.7 Ga) and found positive Δ³³S (1.40–1.80‰) in four meta-turbidites and negative Δ³³S (−0.80‰ and −0.66‰) in two meta-carbonates. Two meta-basalts do not display significant mass-independent fractionation (MIF, −0.01‰ and 0.16‰). In situ Re–Os dating on a molybdenite vein hosted in the meta-turbidites identifies an early ca. 3.7 Ga hydrothermal phase, and in situ Rb–Sr dating of micas in the meta-carbonates suggests metamorphism affected the rocks at ca. 2.2 and 1.7 Ga. We discuss alteration mechanisms and conclude that there is most likely a primary MIF-bearing phase in these meta-sediments. Our new method is therefore a useful addition to the geochemical toolbox, and it confirms that organisms at that time, if present, may indeed have been fed by volcanic nutrients.Jane E. Macdonald, Patrick Sugden, Matthew Dumont, Kristoffer Szilas, Stijn Glorie, Alexander Simpson, Sarah Gilbert, Andrea Burke, Eva E. Stüeke

Nitrogen Isotopes

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