Electron transport measurements in liquid xenon with Xenoscope, a large-scale DARWIN demonstrator

The DARWIN observatory is a proposed next-generation experiment with 40 tonnes of liquid xenon as an active target in a time projection chamber. To study challenges related to the construction and operation of a multi-tonne scale detector, we have designed and constructed a vertical, full-scale demonstrator for the DARWIN experiment at the University of Zurich. Here, we present the first results from a several-months run with 343 kg of xenon and electron drift lifetime and transport measurements with a 53 cm tall purity monitor immersed in the cryogenic liquid. After 88 days of continuous purification, the electron lifetime reached a value of ( 664 ± 23 ) μ s . We measured the drift velocity of electrons for electric fields in the range (25-75) V/cm, and found values consistent with previous measurements. We also calculated the longitudinal diffusion constant of the electron cloud in the same field range, and compared with previous data, as well as with predictions from an empirical model.

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.

Material radiopurity control in the XENONnT experiment

The selection of low-radioactive construction materials is of the utmost importance for rare-event searches and thus critical to the XENONnT experiment. Results of an extensive radioassay program are reported, in which material samples have been screened with gamma-ray spectroscopy, mass spectrometry, and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{222}$$\end{document}222Rn emanation measurements. Furthermore, the cleanliness procedures applied to remove or mitigate surface contamination of detector materials are described. Screening results, used as inputs for a XENONnT Monte Carlo simulation, predict a reduction of materials background (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\sim $$\end{document}∼17%) with respect to its predecessor XENON1T. Through radon emanation measurements, the expected \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{222}$$\end{document}222Rn activity concentration in XENONnT is determined to be 4.2 (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$^{+0.5}_{-0.7}$$\end{document}-0.7+0.5) \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\upmu $$\end{document}μBq/kg, a factor three lower with respect to XENON1T. This radon concentration will be further suppressed by means of the novel radon distillation system.

222 Rn emanation measurements for the XENON1T experiment

The selection of low-radioactive construction materials is of utmost importance for the success of low-energy rare event search experiments. Besides radioactive contaminants in the bulk, the emanation of radioactive radon atoms from material surfaces attains increasing relevance in the effort to further reduce the background of such experiments. In this work, we present the 222 Rn emanation measurements performed for the XENON1T dark matter experiment. Together with the bulk impurity screening campaign, the results enabled us to select the radio-purest construction materials, targeting a 222 Rn activity concentration of 10 μ Bq / kg in 3.2 t of xenon. The knowledge of the distribution of the 222 Rn sources allowed us to selectively eliminate problematic components in the course of the experiment. The predictions from the emanation measurements were compared to data of the 222 Rn activity concentration in XENON1T. The final 222 Rn activity concentration of ( 4.5 ± 0.1 ) μ Bq / kg in the target of XENON1T is the lowest ever achieved in a xenon dark matter experiment.

Search for Coherent Elastic Scattering of Solar ^{8}B Neutrinos in the XENON1T Dark Matter Experiment

We report on a search for nuclear recoil signals from solar ^{8}B neutrinos elastically scattering off xenon nuclei in XENON1T data, lowering the energy threshold from 2.6 to 1.6  keV. We develop a variety of novel techniques to limit the resulting increase in backgrounds near the threshold. No significant ^{8}B neutrinolike excess is found in an exposure of 0.6  t×y. For the first time, we use the nondetection of solar neutrinos to constrain the light yield from 1-2 keV nuclear recoils in liquid xenon, as well as nonstandard neutrino-quark interactions. Finally, we improve upon world-leading constraints on dark matter-nucleus interactions for dark matter masses between 3 and 11  GeV c^{-2} by as much as an order of magnitude.

Light Dark Matter Search with Ionization Signals in XENON1T

We report constraints on light dark matter (DM) models using ionization signals in the XENON1T experiment. We mitigate backgrounds with strong event selections, rather than requiring a scintillation signal, leaving an effective exposure of (22±3) tonne day. Above ∼0.4  keV_{ee}, we observe <1  event/(tonne day keV_{ee}), which is more than 1000 times lower than in similar searches with other detectors. Despite observing a higher rate at lower energies, no DM or CEvNS detection may be claimed because we cannot model all of our backgrounds. We thus exclude new regions in the parameter spaces for DM-nucleus scattering for DM masses m_{χ} within 3-6  GeV/c^{2}, DM-electron scattering for m_{χ}>30  MeV/c^{2}, and absorption of dark photons and axionlike particles for m_{χ} within 0.186-1  keV/c^{2}.

Search for Light Dark Matter Interactions Enhanced by the Migdal Effect or Bremsstrahlung in XENON1T

Direct dark matter detection experiments based on a liquid xenon target are leading the search for dark matter particles with masses above ∼5  GeV/c^{2}, but have limited sensitivity to lighter masses because of the small momentum transfer in dark matter-nucleus elastic scattering. However, there is an irreducible contribution from inelastic processes accompanying the elastic scattering, which leads to the excitation and ionization of the recoiling atom (the Migdal effect) or the emission of a bremsstrahlung photon. In this Letter, we report on a probe of low-mass dark matter with masses down to about 85  MeV/c^{2} by looking for electronic recoils induced by the Migdal effect and bremsstrahlung using data from the XENON1T experiment. Besides the approach of detecting both scintillation and ionization signals, we exploit an approach that uses ionization signals only, which allows for a lower detection threshold. This analysis significantly enhances the sensitivity of XENON1T to light dark matter previously beyond its reach.

Transcriptome-wide analysis of differential gene expression in response to light:dark cycles in a model cnidarian

Animals respond to diurnal shifts in their environment with a combination of behavioral, physiological, and molecular changes to synchronize with regularly-timed external cues. Reproduction, movement, and metabolism in cnidarians have all been shown to be regulated by diurnal lighting, but the molecular mechanisms that may be responsible for these phenotypes remain largely unknown. The starlet sea anemone, Nematostella vectensis, has oscillating patterns of locomotion and respiration, as well as the molecular components of a putative circadian clock that may provide a mechanism for these light-induced responses. Here, we compare transcriptomic responses of N. vectensis when cultured under a diurnal lighting condition (12 h light: 12 h dark) with sea anemones cultured under constant darkness for 20 days. More than 3,000 genes (~13% of transcripts) had significant differences in expression between light and dark, with most genes having higher expression in the photoperiod. Following removal of the light cue 678 genes lost differential expression, suggesting that light-entrained gene expression by the circadian clock has temporal limits. Grouping of genes differentially expressed in light:dark conditions showed that cell cycle and transcription maintained diel expression in the absence of light, while many of the genes related to metabolism, antioxidants, immunity, and signal transduction lost differential expression without a light cue. Our data highlight the importance of diel light cycles on circadian mechanisms in this species, prompting new hypotheses for the role of photoreception in major biological processes, e.g., metabolism, immunity.

Modelling of the Plastisol Knife Over Roll Coating Process

The knife-over-roll coating process of plastisol formulations for flooring applications has been investigated. The coexistence of smooth spherical PVC particles and rough calcium carbonate aggregates in a Newtonian plasticizer makes this suspension a more complex system than those encountered in the literature. The shear viscosity has been measured with Couette and capillary devices in the wide range of shear rates encountered in the process, resulting in a non-monotonous viscosity curve. A numerical model based on the lubrication approximation theory allows accounting for this non-monotonous behavior. It predicts the deposited thickness, the pressure field between roll and knife and the separating force as a function of the plastisol rheology and the coating parameters.

Daily differential expression of melatonin-related genes and clock genes in rat cumulus-oocyte complex: changes after pinealectomy

This study investigated the maturational stage (immature and mature ovaries) differences of mRNA expression of melatonin-forming enzymes (Aanat and Asmt), melatonin membrane receptors (Mt1 and Mt2) and putative nuclear (Rorα) receptors, and clock genes (Clock, Bmal1, Per1, Per2, Cry1, Cry2) in cumulus-oocyte complexes (COC) from weaning Wistar rats. We also examined the effects of pinealectomy and of melatonin pharmacological replacement on the daily expression of these genes in COC. qRT-PCR analysis revealed that in oocytes, the mRNA expression of Asmt, Mt2, Clock, Bmal1, Per2, and Cry1 were higher (P < 0.05) in immature ovaries than in the mature ones. In cumulus cells, the same pattern of mRNA expression for Asmt, Aanat, Rorα, Clock, Per1, Cry1, and Cry2 genes was observed. In oocytes, pinealectomy altered the daily mRNA expression profiles of Asmt, Mt1, Mt2, Clock, Per1, Cry1, and Cry2 genes. In cumulus cells, removal of the pineal altered the mRNA expression profiles of Mt1, Mt2, Rorα, Aanat, Asmt, Clock, Bmal1, Per2, Cry1, and Cry2 genes. Melatonin treatment partially or completely re-established the daily mRNA expression profiles of most genes studied. The mRNA expression of melatonin-related genes and clock genes in rat COC varies with the maturational stage of the meiotic cellular cycle in addition to the hour of the day. This suggests that melatonin might act differentially in accordance with the maturational stage of cumulus/oocyte complex. In addition, it seems that circulating pineal melatonin is very important in the design of the daily profile of mRNA expression of COC clock genes and genes related to melatonin synthesis and action.

197 EXPRESSION OF MELATONIN-RELATED GENES IN RAT CUMULUS–OOCYTE COMPLEXES

Melatonin is a hormone usually associated with the modulation of circadian rhythms and the regulation of seasonal reproductive function. There is evidence that melatonin acts directly on the regulation of ovary function. The mRNA expression of melatonin membrane receptors genes was detected in mammalian and non-mammalian ovaries. In spite of melatonin receptors and Asmt (limiting enzyme in melatonin biosynthesis) genes being present in cattle cumulus–oocyte complexes (COC), no information regarding rat COC has been reported. The aim of this study was to investigate the expression of melatonin receptor (Mt2) and melatonin synthesis enzyme (Asmt) genes at different meiotic cell cycle stages in COC from 27-day-old female rats. All the procedures involving animals were approved by the Animal Care Committee of the Institute of Biomedical Sciences. To obtain germinal vesicle (GV) immature COC from ovarian follicles, rats were treated with 20 IU equine chorionic gonadotropin (eCG) for induction of follicular development and killed by euthanasia 48 h later. To obtain COC at MII oocyte stage from oviducts, rats were injected with 20 IU of eCG and 48 h later with 20 IU of human chorionic gonadotropin (hCG), and then killed after 14 to 16 h. The oocytes in COC were separated from their cumulus cells by repeated pipetting through a narrow-bore pipette in culture medium. Oocytes and cumulus cells total RNA were isolated using a Trizol reagent (Invitrogen Corp., Carlsbad, CA, USA). Pools of 80 COC per cDNA sample were used. Quantitative real-time PCR (qRT-PCR) was performed (7500 Real-Time PCR System; Applied Biosystems Inc., Foster City, CA, USA) with 25-µL reactions containing 2 µL of cDNA (10 ng µL–1), SYBR green (Power SYBR Green; Applied Biosystems Inc.), and 400 nM specific intron-spanning primers. A set of 10-fold serial dilutions of each internal standard (102 to 106 copies/2 µL) was used to generate a standard curve. Transcript numbers were determined by the system software and normalized using the geometric mean calculated from the reference genes: Actb and Rpl37a. All the results were plotted as the mean ± SEM, and 4 replicates were performed. Unpaired t-test was used to evaluate the cell type (oocyte v. cumulus cells) differences. The qRT-PCR analyses revealed the presence of transcripts of the Mt2 gene only in oocytes from immature (GV) and mature (MII) COC. At both maturational stages, the copy numbers for Asmt in oocytes were significantly higher than in cumulus cells. The results confirm the presence of the Asmt gene in rat COC and suggest the possible involvement of these cells on melatonin biosynthesis. The presence of Mt2 transcript in immature and mature oocytes also suggests the potentially important role of melatonin in regulating the rat meiotic cellular cycle. Research supported by FAPESP.

The role of nucleotide-binding oligomerization domain 2 (Nod2) in initiation of rheumatoid arthritis. (68.7)

The etiology of several inflammatory diseases such as rheumatoid arthritis (RA) remains unknown. Some studies including data from our group, report that the receptor NOD2, a member of NLR family, is overexpressed in synovial fibroblasts of patients with RA. Since NOD2 activation might contribute to the initiation and perpetuation of chronic destructive inflammation in RA, we decided to investigate the role of this receptor in arthritis. Initially, WT and NOD2-/- mice were immunized with mBSA, and arthritis was induced by an i.a. injection of mBSA. Our data shows that knockout NOD2 mice did not develop arthritis, as evidenced by the low number of infiltrating cells into the articular cavity, and that transfer of wild type neutrophils into NOD2-/- mice did not restored the inflammatory status. Additionally, to assess if synovial fluid of RA patients could activate NOD2 in vitro, HEK293-Luciferase-NF-κB cells were transfected with a plasmid encoding the NOD2 receptor, 24 hours later these cells were stimulated with MDP or synovial fluid in different concentrations, osteoarthritis synovial fluid were used as control. Luciferase activity was measured 8 hours after stimulation. We observed that stimulation of NOD2 transfected cells with synovial fluid from RA patients leads to increased luciferase activity, suggesting the NF-κB activation dependent of NOD2 signaling in HEK293 cells. Together, these results suggest that NOD2 receptor has an important role in the pathogenesis of RA.

234 EXPRESSION OF NUCLEAR AND MEMBRANE MELATONIN RECEPTORS GENES AND THE CLOCK GENES IN RAT OOCYTES: PRELIMINARY RESULTS

There is evidence that melatonin acts directly on the regulation of ovary function. This action is probably attributed in part to melatonin receptors, which are known to be present in granulosa and cumulus cells (Kang J-T et al. 2009 J. Pineal Res. 46, 22–28). Melatonin is also known to be associated with the modulation of circadian rhythms and the regulation of seasonal reproductive function (Arendt J 1998 Rev. Reprod. 3, 13–22). Circadian rhythms and clock genes appear to be involved in reproductive processes (Dolatshad H et al. 2009 Repro. Fertil. Dev. 21, 1–9). However, the presence of melatonin receptor genes and the clock genes has not been so widely studied or has never been reported to exist in mammalian oocytes.The aim of this study was to investigate the presence of nuclear (Rorα) and membrane (Mt1 and Mt2) melatonin receptors genes and the clock genes (Clock, Bmal1, Cry1, Cry21, Per1, Per2) in rat oocytes by reverse RT-PCR. Twenty-seven-day-old Wistar female rats were treated with 20 UI of pregnant mares serum gonadotropin for induction of follicular development and slaughtered 48 h later. All the procedures involving animals were approved by the Animal Care Committee of the Institute of Biomedical Sciences. The ovaries were removed and placed in TCM-199 supplemented with 100 UI mL-1 penicillin, 100 μg mL-1 streptomycin, and 0.1% polyvinyl alcohol (H-199 medium). Germinal vesicle-intact oocytes, isolated from the ovarian follicles, were denuded from cumulus cells by vortexing for 5 to 8 min. The denuded oocytes were incubated for 5 min in H-199 medium with 0.1% pronase for removal of the zona pellucida. Pools of 80 oocytes per cDNA sample were used.As an internal control for the sample integrity, additional primers for RPL37a were included in each PCR reaction. All the 3 control PCR replicates showed a repeatable amplification. Polymerase chain reaction amplifications of cDNA yielded Rorα, Clock, Bmal1, and Cry1 products in 2 of 3 replicates. No expression of the MT1 and MT2 mRNA was observed. The preliminary results suggest the presence of a nuclear melatonin receptor gene and some clock genes in rat oocytes. However, additional studies are necessary to confirm this hypothesis. This research was supported by FAPESP.

Modeling perceptual learning with multiple interacting elements: a neural network model describing early visual perceptual learning

We introduce a neural network model of an early visual cortical area, in order to understand better results of psychophysical experiments concerning perceptual learning during odd element (pop-out) detection tasks (Ahissar and Hochstein, 1993, 1994a). The model describes a network, composed of orientation selective units, arranged in a hypercolumn structure, with receptive field properties modeled from real monkey neurons. Odd element detection is a final pattern of activity with one (or a few) salient units active. The learning algorithm used was the Associative reward-penalty (Ar-p) algorithm of reinforcement learning (Barto and Anandan, 1985), following physiological data indicating the role of supervision in cortical plasticity. Simulations show that network performance improves dramatically as the weights of inter-unit connections reach a balance between lateral iso-orientation inhibition, and facilitation from neighboring neurons with different preferred orientations. The network is able to learn even from chance performance, and in the presence of a large amount of noise in the response function. As additional tests of the model, we conducted experiments with human subjects in order to examine learning strategy and test model predictions.

Frequent expression of growth factors for mesenchymal cells in human mammary carcinoma cell lines

The expression of growth factors for mesenchymal cells was investigated in 10 different human mammary carcinoma cell lines. Expression of mRNA for platelet-derived growth factor (PDGF) A-chain, PDGF B-chain, transforming growth factor-alpha, and insulin-like growth factor II were found in eight, nine, five, and two of the cell lines, respectively. The production of PDGF-like growth factors by the mammary carcinoma cell lines was investigated in detail. PDGF receptor competing activity and mitogenic activity, which could be neutralized by PDGF antibodies, were found in the conditioned medium of almost all the cell lines. A PDGF-like growth factor was partially purified from the conditioned medium of one of the cell lines, MCF7. A Mr 31,000 component, which was reduced to Mr 17,000, was furthermore precipitated by a PDGF antiserum from the conditioned medium of metabolically labeled MCF7 cells. These results indicate that growth factors for mesenchymal cells are frequently expressed in human mammary carcinoma cell lines. This is of interest in relation to the fact that mammary carcinoma tumors often contain a high proportion of proliferating connective tissue cells.