First Dark Matter Search with Nuclear Recoils from the XENONnT Experiment.

We report on the first search for nuclear recoils from dark matter in the form of weakly interacting massive particles (WIMPs) with the XENONnT experiment, which is based on a two-phase time projection chamber with a sensitive liquid xenon mass of 5.9 ton. During the (1.09±0.03) ton yr exposure used for this search, the intrinsic ^{85}Kr and ^{222}Rn concentrations in the liquid target are reduced to unprecedentedly low levels, giving an electronic recoil background rate of (15.8±1.3) events/ton yr keV in the region of interest. A blind analysis of nuclear recoil events with energies between 3.3 and 60.5 keV finds no significant excess. This leads to a minimum upper limit on the spin-independent WIMP-nucleon cross section of 2.58×10^{-47} cm^{2} for a WIMP mass of 28 GeV/c^{2} at 90% confidence level. Limits for spin-dependent interactions are also provided. Both the limit and the sensitivity for the full range of WIMP masses analyzed here improve on previous results obtained with the XENON1T experiment for the same exposure.

Searching for Heavy Dark Matter near the Planck Mass with XENON1T.

Multiple viable theoretical models predict heavy dark matter particles with a mass close to the Planck mass, a range relatively unexplored by current experimental measurements. We use 219.4 days of data collected with the XENON1T experiment to conduct a blind search for signals from multiply interacting massive particles (MIMPs). Their unique track signature allows a targeted analysis with only 0.05 expected background events from muons. Following unblinding, we observe no signal candidate events. This Letter places strong constraints on spin-independent interactions of dark matter particles with a mass between 1×10^{12} and 2×10^{17} GeV/c^{2}. In addition, we present the first exclusion limits on spin-dependent MIMP-neutron and MIMP-proton cross sections for dark matter particles with masses close to the Planck scale.

Search for New Physics in Electronic Recoil Data from XENONnT.

We report on a blinded analysis of low-energy electronic recoil data from the first science run of the XENONnT dark matter experiment. Novel subsystems and the increased 5.9 ton liquid xenon target reduced the background in the (1, 30) keV search region to (15.8±1.3) events/(ton×year×keV), the lowest ever achieved in a dark matter detector and ∼5 times lower than in XENON1T. With an exposure of 1.16 ton-years, we observe no excess above background and set stringent new limits on solar axions, an enhanced neutrino magnetic moment, and bosonic dark matter.

Effects of fatty acids, nucleotides and reactive oxygen species on durum wheat mitochondria.

Linoleic acid (LA) and other fatty acids added to respiring durum wheat mitochondria (DWM) were found to cause a remarkable membrane potential (deltaPsi) decrease, as monitored by measuring safranin fluorescence. The rate of deltaPsi decrease showed (i) saturation dependence on LA concentration; (ii) fatty acid specificity; (iii) inhibition by externally added ATP, GDP, GTP and Mg(2+) and (iv) sigmoid dependence upon initial DeltaPsi, thus suggesting the existence of an active plant mitochondrial uncoupling protein (PUMP) in mitochondria from monocotyledonous species (durum wheat, Triticum durum Desf.). Surprisingly, the rate of the linoleate dependent DeltaPsi decrease was found to be activated by reactive oxygen species (ROS) (hydrogen peroxide and superoxide anion) and, moreover, linoleate proved to lower the mitochondrial generation of superoxide anion. These results suggest that ROS can activate PUMP, thus protecting the cell against mitochondrial ROS production.

Release of matrix proteins from mitochondria to cytosol during the prereplicative phase of liver regeneration.

70% partial hepatectomy (PH) in the rat causes a release, into the cytosolic fraction, of mitochondrial matrix proteins, namely the mitochondrial isoform of aspartate aminotransferase (mAAT) and malate dehydrogenase (MDH), during the first 24 h after PH, when no growth of the residual liver is observed. After this time interval, the weight of the liver starts to increase and the normal weight is reached at 96 h after PH. This proliferative phase is characterized by a progressive recovery of the normal levels of intramitochondrial activities of mAAT and MDH. Mitochondria isolated at 24 h after PH show a membrane permeabilization to sucrose accompanied by a release of matrix enzymes; both are blocked by cyclosporin A. These results suggest an alteration of mitochondrial membrane integrity, during the prereplicative phase of liver regeneration, with the occurrence of an increased permeability that allows the passage into the cytosol of matrix enzymes.