302 research outputs found

    New limit on neutrinoless double β decay in ^(136)Xe with a time projection chamber

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    A xenon time projection chamber with an active volume of 207 L has been built to study neutrinoless double β decay in ^(136)Xe. Data were taken in the Gotthard Underground Laboratory, with 5 atm of xenon enriched to 62.5% in ^(136)Xe. From 3380 h of data, no evidence has been found for the 0ν 0^(+)→0^(+) transition. Half-life limits of T_(1/2)^(0ν)>2.5(4.9)×10^(23) yr in the mass-mechanism mode and T_(1/2)^(0ν)>1.7(3.2)×10^(23) yr in the right-handed-current mode, at the 90(68)% C.L., were derived. An upper limit for the Majorana neutrino mass parameter was deduced

    Search for neutrinoless double-beta decay in 136-Xe with a time projection chamber

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    A xenon time projection chamber (TPC) with an active volume of 180 liters has been built to study neutrinoless double-beta decay in Xe-136. The experiment was performed in the Gotthard Underground Laboratory, with 5 atm of xenon enriched to 62.5% in Xe-136. The experimental details, background considerations, detector performance, and data analysis are discussed. From 6830 h of data, no evidence has been found for the 0nu 0+-->0+ transition. Half-life limits of T1/2(0nu) > 3.4(6.4) X 10^(23) yr in the mass mechanism mode, and T1/2(0nu) > 2.6(4.9) X 10^23 yr in the right-handed currents mode, at the 90(68)% C.L., were derived, corresponding to an upper limit on the Majorana neutrino mass parameter [m(nu)] of about 2.8 eV. Limits on two-neutrino double-beta decay of T1/2(2nu) /2 > 2. 1 X 10^(20) yr, and on neutrinoless double-beta decay with Majoron emission of T1/2(0nuchi) > 4.9 X 10^(21) yr, both at 90% C.L., were also derived. Accordingly, a limit on the effective Majoron-neutrino coupling parameter of [g(M)] < 2.4 X 10^(-4) was deduced

    Characterization of an extracellular lipase and its chaperone from Ralstonia eutropha H16

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    Lipase enzymes catalyze the reversible hydrolysis of triacylglycerol to fatty acids and glycerol at the lipid–water interface. The metabolically versatile Ralstonia eutropha strain H16 is capable of utilizing various molecules containing long carbon chains such as plant oil, organic acids, or Tween as its sole carbon source for growth. Global gene expression analysis revealed an upregulation of two putative lipase genes during growth on trioleate. Through analysis of growth and activity using strains with gene deletions and complementations, the extracellular lipase (encoded by the lipA gene, locus tag H16_A1322) and lipase-specific chaperone (encoded by the lipB gene, locus tag H16_A1323) produced by R. eutropha H16 was identified. Increase in gene dosage of lipA not only resulted in an increase of the extracellular lipase activity, but also reduced the lag phase during growth on palm oil. LipA is a non-specific lipase that can completely hydrolyze triacylglycerol into its corresponding free fatty acids and glycerol. Although LipA is active over a temperature range from 10 °C to 70 °C, it exhibited optimal activity at 50 °C. While R. eutropha H16 prefers a growth pH of 6.8, its extracellular lipase LipA is most active between pH 7 and 8. Cofactors are not required for lipase activity; however, EDTA and EGTA inhibited LipA activity by 83 %. Metal ions Mg[superscript 2+], Ca[superscript 2+], and Mn[superscript 2+] were found to stimulate LipA activity and relieve chelator inhibition. Certain detergents are found to improve solubility of the lipid substrate or increase lipase-lipid aggregation, as a result SDS and Triton X-100 were able to increase lipase activity by 20 % to 500 %. R. eutropha extracellular LipA activity can be hyper-increased, making the overexpression strain a potential candidate for commercial lipase production or in fermentations using plant oils as the sole carbon source.Malaysia-MIT Biotechnology Partnership Programm

    A Re-Evaluation of the nuclear Structure Function Ratios for D, He, Li, C and Ca

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    We present a re-evaluation of the structure function ratios F2(He)/F2(D), F2(C)/F2(D) and F2(Ca)/F2(D) measured in deep inelastic muon-nucleus scattering at an incident muon momentum of 200 GeV. We also present the ratios F2(C)/F2(Li), F2(Ca)/F2(Li) and F2(Ca)/F2(C) measured at 90 GeV. The results are based on data already published by NMC; the main difference in the analysis is a correction for the masses of the deuterium targets and an improvement in the radiative corrections. The kinematic range covered is 0.0035 < x < 0.65, 0.5 < Q^2 <90 GeV^2 for the He/D, C/D and Ca/D data and 0.0085 < x < 0.6, 0.84 < Q^2 < 17 GeV^2 for the Li/C/Ca ones.Comment: 6 pages, Latex, 3 figures as uuencoded compressed tar file included at the end, in case of problems contact [email protected] (Antje Bruell

    Sp6 and Sp8 transcription factors control AER formation and dorsal-ventral patterning in limb development

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    The formation and maintenance of the apical ectodermal ridge (AER) is critical for the outgrowth and patterning of the vertebrate limb. The induction of the AER is a complex process that relies on integrated interactions among the Fgf, Wnt, and Bmp signaling pathways that operate within the ectoderm and between the ectoderm and the mesoderm of the early limb bud. The transcription factors Sp6 and Sp8 are expressed in the limb ectoderm and AER during limb development. Sp6 mutant mice display a mild syndactyly phenotype while Sp8 mutants exhibit severe limb truncations. Both mutants show defects in AER maturation and in dorsal-ventral patterning. To gain further insights into the role Sp6 and Sp8 play in limb development, we have produced mice lacking both Sp6 and Sp8 activity in the limb ectoderm. Remarkably, the elimination or significant reduction in Sp6;Sp8 gene dosage leads to tetra-amelia; initial budding occurs, but neither Fgf8 nor En1 are activated. Mutants bearing a single functional allele of Sp8 (Sp6-/-;Sp8+/-) exhibit a split-hand/foot malformation phenotype with double dorsal digit tips probably due to an irregular and immature AER that is not maintained in the center of the bud and on the abnormal expansion of Wnt7a expression to the ventral ectoderm. Our data are compatible with Sp6 and Sp8 working together and in a dose-dependent manner as indispensable mediators of Wnt/βcatenin and Bmp signaling in the limb ectoderm. We suggest that the function of these factors links proximal-distal and dorsal-ventral patterning
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