Approaching the Gamow Window with Stored Ions : Direct Measurement of Xe 124 (p,γ) in the ESR Storage Ring

© 2019 American Physical Society. All rights reserved.We report the first measurement of low-energy proton-capture cross sections of Xe124 in a heavy-ion storage ring. Xe12454+ ions of five different beam energies between 5.5 and 8 AMeV were stored to collide with a windowless hydrogen target. The Cs125 reaction products were directly detected. The interaction energies are located on the high energy tail of the Gamow window for hot, explosive scenarios such as supernovae and x-ray binaries. The results serve as an important test of predicted astrophysical reaction rates in this mass range. Good agreement in the prediction of the astrophysically important proton width at low energy is found, with only a 30% difference between measurement and theory. Larger deviations are found above the neutron emission threshold, where also neutron and γ widths significantly impact the cross sections. The newly established experimental method is a very powerful tool to investigate nuclear reactions on rare ion beams at low center-of-mass energies.Peer reviewedFinal Published versio

Characterization of the QUartz Photon Intensifying Detector (QUPID) for Noble Liquid Detectors

Dark Matter and Double Beta Decay experiments require extremely low radioactivity within the detector materials. For this purpose, the University of California, Los Angeles and Hamamatsu Photonics have developed the QUartz Photon Intensifying Detector (QUPID), an ultra-low background photodetector based on the Hybrid Avalanche Photo Diode (HAPD) and entirely made of ultraclean synthetic fused silica. In this work we present the basic concept of the QUPID and the testing measurements on QUPIDs from the first production line. Screening of radioactivity at the Gator facility in the Laboratori Nazionali del Gran Sasso has shown that the QUPIDs safely fulfill the low radioactive contamination requirements for the next generation zero background experiments set by Monte Carlo simulations. The quantum efficiency of the QUPID at room temperature is > 30% at the xenon scintillation wavelength. At low temperatures, the QUPID shows a leakage current less than 1 nA and a global gain of 10^5. In these conditions, the photocathode and the anode show > 95% linearity up to 1 uA for the cathode and 3 mA for the anode. The photocathode and collection efficiency are uniform to 80% over the entire surface. In parallel with single photon counting capabilities, the QUPIDs have a good timing response: 1.8 +/- 0.1 ns rise time, 2.5 +/- 0.2 ns fall time, 4.20 +/- 0.05 ns pulse width, and 160 +/- 30 ps transit time spread. The QUPIDs have also been tested in a liquid xenon environment, and scintillation light from 57Co and 210Po radioactive sources were observed.Comment: 15 pages, 22 figure

Remodeling the Proteostasis Network to Rescue Glucocerebrosidase Variants by Inhibiting ER-Associated Degradation and Enhancing ER Folding

Gaucher’s disease (GD) is characterized by loss of lysosomal glucocerebrosidase (GC) activity. Mutations in the gene encoding GC destabilize the protein’s native folding leading to ER-associated degradation (ERAD) of the misfolded enzyme. Enhancing the cellular folding capacity by remodeling the proteostasis network promotes native folding and lysosomal activity of mutated GC variants. However, proteostasis modulators reported so far, including ERAD inhibitors, trigger cellular stress and lead to induction of apoptosis. We show herein that lacidipine, an L-type Ca2+ channel blocker that also inhibits ryanodine receptors on the ER membrane, enhances folding, trafficking and lysosomal activity of the most severely destabilized GC variant achieved via ERAD inhibition in fibroblasts derived from patients with GD. Interestingly, reprogramming the proteostasis network by combining modulation of Ca2+ homeostasis and ERAD inhibition remodels the unfolded protein response and dramatically lowers apoptosis induction typically associated with ERAD inhibition

Enzymatic Blockade of the Ubiquitin-Proteasome Pathway

Ubiquitin-dependent processes control much of cellular physiology. We show that expression of a highly active, Epstein-Barr virus-derived deubiquitylating enzyme (EBV-DUB) blocks proteasomal degradation of cytosolic and ER-derived proteins by preemptive removal of ubiquitin from proteasome substrates, a treatment less toxic than the use of proteasome inhibitors. Recognition of misfolded proteins in the ER lumen, their dislocation to the cytosol, and degradation are usually tightly coupled but can be uncoupled by the EBV-DUB: a misfolded glycoprotein that originates in the ER accumulates in association with cytosolic chaperones as a deglycosylated intermediate. Our data underscore the necessity of a DUB activity for completion of the dislocation reaction and provide a new means of inhibition of proteasomal proteolysis with reduced cytotoxicity.National Institutes of Health (U.S.)EMBO (long term Fellowship 2008-379)Boehringer Ingelheim Fond

Wiskott-Aldrich syndrome protein deficiency in innate immune cells leads to mucosal immune dysregulation and colitis in mice

BACKGROUND & AIMS: Immunodeficiency and autoimmune sequelae, including colitis, develop in patients and mice deficient in Wiskott-Aldrich Syndrome protein (WASP), a hematopoietic-specific intracellular signaling molecule that regulates the actin cytoskeleton. Development of colitis in WASP-deficient mice requires lymphocytes; transfer of T cells is sufficient to induce colitis in immunodeficient mice. We investigated the interactions between innate and adaptive immune cells in mucosal regulation during development of T-cell-mediated colitis in mice with WASP-deficient cells of the innate immune system. METHODS: Naïve and/or regulatory CD4(+) T cells were transferred from 129 SvEv mice into RAG-2 deficient (RAG-2 KO) mice or mice lacking WASP and RAG-2 (WRDKO). Animals were observed for the development of colitis; effector and regulatory functions of innate immune and T cells were analyzed with in vivo and in vitro assays. RESULTS: Transfer of unfractionated CD4(+) T cells induced severe colitis in WRDKO, but not RAG-2 KO, mice. Naïve wild-type T cells had higher levels of effector activity and regulatory T cells had reduced suppressive function when transferred into WRDKO mice compared to RAG-2 KO mice. Regulatory T-cell proliferation, generation, and maintenance of FoxP3 expression were reduced in WRDKO recipients, and associated with reduced numbers of CD103(+) tolerogenic dendritic cells and levels of interleukin (IL)-10. Administration of IL-10 prevented induction of colitis following transfer of T cells into WRDKO mice. CONCLUSIONS: Defective interactions between WASP-deficient innate immune cells and normal T cells disrupt mucosal regulation, potentially by altering the functions of tolerogenic dendritic cells, production of IL-10, and homeostasis of regulatory T cells

⁶³Cu(n,γ ) cross section measured via 25 keV activation and time of flight

In the nuclear mass range A≈60 to 90 of the solar abundance distribution the weak s-process component is the dominant contributor. In this scenario, which is related to massive stars, the overall neutron exposure is not sufficient for the s process to reach mass flow equilibrium. Hence, abundances and isotopic ratios are very sensitive to the neutron capture cross sections of single isotopes, and nucleosynthesis models need accurate experimental data. In this work we report on a new measurement of the Cu63(n,γ) cross section for which the existing experimental data show large discrepancies. The Cu63(n,γ) cross section at kBT=25 keV was determined via activation with a quasistellar neutron spectrum at the Joint Research Centre (JRC) in Geel, and the energy dependence was determined with the time-of-flight technique and the calorimetric 4πBaF2 detector array DANCE at the Los Alamos National Laboratory. We provide new cross section data for the whole astrophysically relevant energy range

Thermal (n, γ) cross section and resonance integral of 171Tm

Background: About 50% of the heavy elements are produced in stars during the slow neutron capture process. The analysis of branching points allows us to set constraints on the temperature and the neutron density in the interior of stars. Purpose: The temperature dependence of the branch point 171Tm is weak. Hence, the 171Tm neutron capture cross section can be used to constrain the neutron density during the main component of the s process in thermally pulsing asymptotic giant branch (TP-AGB) stars. Methods: A 171Tm sample produced at the ILL was activated with thermal and epithermal neutrons at the TRIGA research reactor at the Johannes Gutenberg-Universität Mainz. Results: The thermal neutron capture cross section and the resonance integral have been measured for the first time to be σth = 9.9 ± 0.9 b and σRI = 193 ± 14 b. Conclusions: Based on our results, new estimations of the direct capture components’ impact on the Maxwellian-nAveraged cross sections (MACS) are possible.European Unions’s Seventh Framework Programme (FP/2007-2013

Simulations of the High-Energy Beam-Transport (HEBT) section at FRANZ

The neutron source FRANZ (Frankfurter Neutronenquelle am Stern-Gerlach-Zentrum), which is currently under construction, will be the neutron source with the highest intensity in the nuclear-astrophysically relevant energy region. The TraceWin code was used to design the High-Energy Beam-Transport section with regard to the experimental requirements at different target positions

Analysis of Protease Activity in Live Antigen-presenting Cells Shows Regulation of the Phagosomal Proteolytic Contents During Dendritic Cell Activation

Here, we describe a new approach designed to monitor the proteolytic activity of maturing phagosomes in live antigen-presenting cells. We find that an ingested particle sequentially encounters distinct protease activities during phagosomal maturation. Incorporation of active proteases into the phagosome of the macrophage cell line J774 indicates that phagosome maturation involves progressive fusion with early and late endocytic compartments. In contrast, phagosome biogenesis in bone marrow–derived dendritic cells (DCs) and macrophages preferentially involves endocytic compartments enriched in cathepsin S. Kinetics of phagosomal maturation is faster in macrophages than in DCs. Furthermore, the delivery of active proteases to the phagosome is significantly reduced after the activation of DCs with lipopolysaccharide. This observation is in agreement with the notion that DCs prevent the premature destruction of antigenic determinants to optimize T cell activation. Phagosomal maturation is therefore a tightly regulated process that varies according to the type and differentiation stage of the phagocyte

Neutron activation of 69^{69}Ga and 71^{71}Ga at kBT≈25 keV

Background: About 50% of heavy elements are produced by the slow neutron capture process (s process) in stars. The element gallium is mostly produced during the weak s process in massive stars. Purpose: Our activation at k$_{B}$T≈25 keV is the first experiment in a series of activation and time-of-flight measurements on $^{69}$Ga and $^{71}$Ga relevant for astrophysics. Methods: We activated $^{69}$Ga and $^{71}$Ga with a neutron distribution that corresponds to a quasistellar distribution with k$_{B}$T=25 keV at the Joint Research Centre (JRC), Geel, Belgium. Protons were provided by an electrostatic Van de Graaff accelerator to produce neutrons via the reaction $^{7}$Li(p,n). The produced activity was measured via the γ emission by the decaying product nuclei by high-purity germanium detectors. Results: We provide spectrum-averaged cross sections (SACS) and ratios of the cross sections σ$_{Ga}$/σ$_{Au}$ for the neutron spectrum of the activation. We obtain values of σ$_{69Ga,SACS}$=(186±12) mb and σ$_{71GA,SACS}$ = (112±7) mb, and cross section ratios of σ$_{69Ga}$/σ$_{Au}$=0.29±0.02 and σ$_{71Ga}$/σ$_{Au}$ = 0.17±0.01. Conclusions: Our data disagree with the available evaluated data provided by KADoNiS v0.3, our cross-section ratio is about 20% higher for $^{69}$Ga and about 20% lower for $^{71}$Ga