We present results from the first phase of the KamLAND-Zen double-beta decay experiment, corresponding to an exposure of 89.5 kg yr of 136 Xe. We obtain a lower limit for the neutrinoless double-beta decay half-life of T 0ν 1/2 > 1.9 × 10 25 yr at 90% C.L. The combined results from KamLAND-Zen and EXO-200 give T 0ν 1/2 > 3.4 × 10 25 yr at 90% C.L., which corresponds to a Majorana neutrino mass limit of m ββ < (120 − 250) meV based on a representative range of available matrix element calculations. Using those calculations, this result excludes the Majorana neutrino mass range expected from the neutrinoless double-beta decay detection claim in 76 Ge, reported by a part of the Heidelberg-Moscow Collaboration, at more than 97.5% C.L. 21.10.Tg, 14.60.Pq, 27.60.+j Double-beta (ββ) decay is a rare nuclear process observable in even-even nuclei for which ordinary beta decay is energetically forbidden or highly suppressed by large spin differences. Standard ββ decay proceeds by a second-order weak interaction emitting two electron anti neutrinos and two electrons (2νββ). If, however, the neutrino is a massive Majorana particle, ββ decay might also occur without the emission of neutrinos (0νββ). Observation of such a process would demonstrate that lepton number is not conserved in nature. Moreover, if the process is mediated by the exchange of a light left-handed neutrino, its rate increases with the square of the effective Majorana neutrino mass m ββ ≡ Σ i U 2 ei m νi , and hence its measurement would provide information on the absolute neutrino mass scale. To date there has been only one claimed observation of 0νββ decay, in 76 Ge [1].At present there are several operating experiments performing 0νββ decay searches with design sensitivities sufficient to test the Majorana neutrino mass implied by the claim in [1] within a few years of running: GERDA with 76 Ge, CUORE-0 with 130 Te, and EXO-200 and KamLAND-Zen with 136 Xe. Among those experiments, KamLAND-Zen released its first 0νββ half-life limit, T 0ν 1/2 > 5.7 × 10 24 yr at 90% C.L., based on a 27.4 kg yr exposure [2]. Although the sensitivity of this result was impeded by the presence of an unexpected background peak just above the 2.458 MeV Q value of 136 Xe ββ decay, the Majorana neutrino mass sensitivity was similar to that in Ref. [1]. EXO-200 later improved on this limit by a factor of 2.8 [3], constraining the result in [1] for a number of nuclear matrix element (NME) calculations.As shown below, we have found the problematic background peak in the KamLAND-Zen spectrum to most likely come from metastable 110m Ag. We embarked recently on a purification campaign to remove this isotope. Doing so required extracting the Xe from the detector, thus marking the end of the first phase of KamLAND-Zen. In this Letter we report on the full data set from the first phase of KamLAND-Zen, corresponding to an exposure of 89.5 kg yr of 136 Xe. This represents a factor of 3.2 increase over KamLAND-Zen's first result [2], and is also the largest exposure for a ββ decay isot...

We present results from the KamLAND-Zen double-beta decay experiment based on an exposure of 77.6 days with 129 kg of 136 Xe. The measured two-neutrino double-beta decay half-life of 136 Xe is T 2ν 1/2 = 2.38 ± 0.02(stat) ± 0.14(syst) × 10 21 yr, consistent with a recent measurement by EXO-200. We also obtain a lower limit for the neutrinoless double-beta decay half-life, T 0ν 1/2 > 5.7 × 10 24 yr at 90% confidence level (C.L.), which corresponds to almost a five-fold improvement over previous limits.

IsdG and IsdI from Staphylococcus aureus are novel heme degrading enzymes containing unusually non-planar (ruffled) heme. While canonical heme degrading enzymes, heme oxygenases, catalyze heme degradation coupled with the release of CO, in this study we demonstrate that the primary C1 product of the S. aureus enzymes is formaldehyde. This finding clearly reveals that both IsdG and IsdI degrade heme by an unusual mechanism distinct from the well-characterized heme oxygenase mechanism as recently proposed for MhuD from Mycobacterium tuberculosis. We conclude that heme ruffling is critical for the drastic mechanistic change for these novel bacterial enzymes.

We present limits on Majoron-emitting neutrinoless double-beta decay modes based on an exposure of 112.3 days with 125 kg of 136 Xe. In particular, a lower limit on the ordinary (spectral index n = 1) Majoronemitting decay half-life of 136 Xe is obtained as T 0νχ 0 1/2 > 2.6 × 10 24 yr at 90% C.L., a factor of five more stringent than previous limits. The corresponding upper limit on the effective Majoron-neutrino coupling, using a range of available nuclear matrix calculations, is gee < (0.8 − 1.6) × 10 −5 . This excludes a previously unconstrained region of parameter space and strongly limits the possible contribution of ordinary Majoron emission modes to 0νββ decay for neutrino masses in the inverted hierarchy scheme.

Renal parenchymal cells as well as renal vessels may produce AM under hypoxic conditions.