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Background and Aim This review investigates the role of gastrointestinal and hepatic manifestations in COVID‐19, particularly with regard to the prevalence of isolated gastrointestinal (GI) symptoms. Methods We searched PubMed, Embase, and Cochrane library for COVID‐19 publications from 1 December 2019 to 18 May 2020. We included any study that reported the presence of GI symptoms in a sample of >5 COVID‐19 patients. Data collection and risk of bias assessment were performed independently by two reviewers. Where ≥3 studies reported data sufficiently similar to allow calculation of a pooled prevalence, we performed random effects meta‐analysis. Results This review included 17 776 COVID‐19 patients from 108 studies. Isolated GI symptoms only occurred in 1% (95% confidence interval [CI] 0–6%) of patients. GI symptoms were reported in 20% (95% CI 15–24%) of patients. The most common were anorexia (21%, 95% CI 15–27%), diarrhea (13%, 95% CI 11–16%), nausea or vomiting (8%, 95% CI 6–11%), and abdominal pain (4%, 95% CI 2–6%). Transaminase elevations were present in 24% (95% CI 17–31%) of patients. Higher prevalence of GI symptoms were reported in studies published after 1st April, with prevalence of diarrhea 16% (95% CI 13–20), nausea or vomiting 12% (95% CI 8–16%), and any GI symptoms 24% (95% CI 18–34%). GI symptoms were associated with severe COVID‐19 disease (odds ratio [OR] 2.1, 95% CI 1.3–3.2), but not mortality (OR 0.90, 95% CI 0.52–1.54). Conclusions Patients with isolated GI symptoms may represent a small but significant portion of COVID‐19 cases. When testing resources are abundant, clinicians should still consider testing patients with isolated GI symptoms or unexplained transaminase elevations for COVID‐19. More recent studies estimate higher overall GI involvement in COVID‐19 than was previously recognized., This review is a systematic review and meta‐analysis to characterize the prevalence of gastrointestinal (GI) and hepatic involvement in COVID‐19 and specifically assess the prevalence of GI symptoms in isolation. This review included 17 776 COVID‐19 patients from 108 studies. Isolated GI symptoms occurred in 1% (95% confidence interval 0–6%) of patients.

Background Combining impedance with pH monitoring improves the detection and characterization of gastro-oesophageal reflux (GOR), yet the two modalities frequently differ in GOR quantification. Ambulatory 24-h pH-impedance monitoring often reveals more significant oesophageal acid exposure than impedance-measured reflux activity in patients with symptomatic gastro-oesophageal reflux disease (GORD). The purpose of this study is to elucidate the discrepancies between these modalities by assessing the predictive accuracy of impedance compared to acid exposure standards. Methods A single-institution, retrospective review of sequential 24-h pH-impedance results of 72 patients with symptomatic GOR off anti-secretory therapy was conducted. Reflux events measured by impedance were stratified by patient position and compared to oesophageal acid exposure time (AET). Oesophageal AET limits for GORD detection were utilized as gold standards to generate serial receiver operator characteristics (ROC) curves to assess the sensitivity and specificity of current impedance GORD detection limits and identify optimized impedance standards based on area under the curve (AUC) analysis. Results Mean total AET time was 10.5% (± 9.9%), and 63.8% of patients had elevated AET. By impedance, median GOR frequency was 43 (IQR 21–68), and 22.2% exceeded conventional GOR frequency limits of normal. ROC curve analysis revealed the current impedance standard of > 73 GOR events has a sensitivity of 32.6% and specificity of 96.5% (AUC 0.74) for GORD detection. By AUC analysis, an impedance threshold of > 41 GOR events is optimal for GORD detection (sensitivity 69.6%, specificity 80.7%, AUC 0.83). Conclusion Conventional impedance standards for abnormal GOR frequency are weakly sensitive for the detection of GORD, providing a possible explanation to discrepancies in AET and impedance interpretation. Lowering impedance-measured GOR frequency limits to > 41 optimizes sensitivity and specificity while increasing congruence between pH and impedance metrics.

International audience; The Ultracold Neutron Asymmetry (UCNA) experiment was designed to measure the β-decay asymmetry parameter, A0, for free neutron decay. In the experiment, polarized ultracold neutrons are transported into a decay trap, and their β-decay electrons are detected with ≈4π acceptance into two detector packages which provide position and energy reconstruction. The experiment also has sensitivity to bn, the Fierz interference term in the neutron β-decay rate. In this work, we determine bn from the energy dependence of A0 using the data taken during the UCNA 2011–2013 run. In addition, we present the same type of analysis using the earlier 2010 A dataset. Motivated by improved statistics and comparable systematic errors compared to the 2010 data-taking run, we present a new bn measurement using the weighted average of our asymmetry dataset fits, to obtain bn=0.066±0.041stat±0.024syst which corresponds to a limit of −0.012

EPJ Web of Conferences, 219, ISSN:2100-014X, ISSN:2101-6275, International Workshop on Particle Physics at Neutron Sources (PPNS 2018), Grenoble, France, May 24–26, 2018, ISBN:978-2-7598-9082-8

A classic electrostatic induction machine, Cavallo's multiplier, is suggested for in situ production of very high voltage in cryogenic environments. The device is suitable for generating a large electrostatic field under conditions of very small load current. Operation of the Cavallo multiplier is analyzed, with quantitative description in terms of mutual capacitances between electrodes in the system. A demonstration apparatus was constructed, and measured voltages are compared to predictions based on measured capacitances in the system. The simplicity of the Cavallo multiplier makes it amenable to electrostatic analysis using finite element software, and electrode shapes can be optimized to take advantage of a high dielectric strength medium such as liquid helium. A design study is presented for a Cavallo multiplier in a large-scale, cryogenic experiment to measure the neutron electric dipole moment., 9 pages, 10 figures

We describe a detection system designed for precise measurements of angular correlations in neutron $\beta$ decay. The system is based on thick, large area, highly segmented silicon detectors developed in collaboration with Micron Semiconductor, Ltd. The prototype system meets specifications for $\beta$ electron detection with energy thresholds below 10 keV, energy resolution of $\sim$3 keV FWHM, and rise time of $\sim$50 ns with 19 of the 127 detector pixels instrumented. Using ultracold neutrons at the Los Alamos Neutron Science Center, we have demonstrated the coincident detection of $\beta$ particles and recoil protons from neutron $\beta$ decay. The fully instrumented detection system will be implemented in the UCNB and Nab experiments, to determine the neutron $\beta$ decay parameters $B$, $a$, and $b$., Comment: Copyright 2016. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/

We have followed up on our previous measurements of upscattering of ultracold neutrons (UCNs) from a series of gases by making measurements of total cross sections on the following gases hydrogen, ethane, methane, isobutene, n-butane, ethylene, water vapor, propane, neopentane, isopropyl alcohol, and ^3He. The values of these cross sections are important for estimating the loss rate of trapped neutrons due to residual gas and are relevant to neutron lifetime measurements using UCNs. The effects of the UCN velocity and path-length distributions were accounted for in the analysis using a Monte Carlo transport code. Results are compared to our previous measurements and with the known absorption cross section for ^3He scaled to our UCN energy. We find that the total cross sections for the hydrocarbon gases are reasonably described by a function linear in the number of hydrogen atoms in the molecule.

We have constructed an apparatus to study DC electrical breakdown in liquid helium at temperatures as low as 0.4 K and at pressures between the saturated vapor pressure and ∼600 Torr. The apparatus can house a set of electrodes that are 12 cm in diameter with a gap of 1–2 cm between them, and a potential up to ±50 kV can be applied to each electrode. Initial results demonstrated that it is possible to apply fields exceeding 100 kV/cm in a 1 cm gap between two electropolished stainless steel electrodes 12 cm in diameter for a wide range of pressures at 0.4 K. We also measured the current between two electrodes. Our initial results, I < 1 pA at 45 kV, correspond to a lower bound on the effective volume resistivity of liquid helium of ρV > 5 × 10^(18) Ω cm. This lower bound is 5 times larger than the bound previously measured. We report the design, construction, and operational experience of the apparatus, as well as initial results.

We report a measurement of the spin-flip probabilities for ultracold neutrons interacting with surfaces coated with nickel phosphorus. For 50~$\mu$m thick nickel phosphorus coated on stainless steel, the spin-flip probability per bounce was found to be $\beta_{\rm NiP\;on\;SS} = (3.3^{+1.8}_{-5.6}) \times 10^{-6}$. For 50~$\mu$m thick nickel phosphorus coated on aluminum, the spin-flip probability per bounce was found to be $\beta_{\rm NiP\;on\;Al} = (3.6^{+2.1}_{-5.9}) \times 10^{-6}$. For the copper guide used as reference, the spin flip probability per bounce was found to be $\beta_{\rm Cu} = (6.7^{+5.0}_{-2.5}) \times 10^{-6}$. The results on the nickel phosphorus-coated surfaces may be interpreted as upper limits, yielding $\beta_{\rm NiP\;on\;SS} < 6.2 \times 10^{-6}$ (90\% C.L.) and $\beta_{\rm NiP\;on\;Al} < 7.0 \times 10^{-6}$ (90\% C.L.) for 50~$\mu$m thick nickel phosphorus coated on stainless steel and 50~$\mu$m thick nickel phosphorus coated on aluminum, respectively. Nickel phosphorus coated stainless steel or aluminum provides a solution when low-cost, mechanically robust, and non-depolarizing UCN guides with a high-Fermi-potential are needed., Comment: 12 pages, 5 figures

A multilayer surface detector for ultracold neutrons (UCNs) is described. The top $^{10}$B layer is exposed to the vacuum chamber and directly captures UCNs. The ZnS:Ag layer beneath the $^{10}$B layer is a few microns thick, which is sufficient to detect the charged particles from the $^{10}$B(n,$\alpha$)$^7$Li neutron-capture reaction, while thin enough so that ample light due to $\alpha$ and $^7$Li escapes for detection by photomultiplier tubes. One-hundred-nm thick $^{10}$B layer gives high UCN detection efficiency, as determined by the mean UCN kinetic energy, detector materials and others. Low background, including negligible sensitivity to ambient neutrons, has also been verified through pulse-shape analysis and comparisons with other existing $^3$He and $^{10}$B detectors. This type of detector has been configured in different ways for UCN flux monitoring, development of UCN guides and neutron lifetime research., Comment: 21 pages, 10 figures

A discovery of a permanent electric dipole moment (EDM) of the neutron would provide one of the most important low energy tests of the discrete symmetries beyond the Standard Model of particle physics. A new search of neutron EDM, to be conducted at the spallation neutron source (SNS) at ORNL, is designed to improve the present experimental limit of ~10^-26 e-cm by two orders of magnitude. The experiment is based on the magnetic-resonance technique in which polarized neutrons precess at the Larmor frequency when placed in a static magnetic field; a non-zero EDM would be evident as a difference in precession frequency when a strong external electric field is applied parallel vs. anti-parallel to the magnetic field. In addition to its role as neutron spin-analyzer via the spin-dependent n+3He nuclear capture reaction, polarized helium-3 (which has negligible EDM) will serve as co-magnetometer to correct for drifts in the magnetic field. In one of the two methods that will be built into the apparatus, the helium-3 precession signal is read out by SQUID-based gradiometers. We present a design study of a SQUID system suitable for the neutron EDM apparatus, and discuss using very long leads between the pickup loop and the SQUID., 5 pages, 3 figures. Submitted to IEEE Transactions on Applied Superconductivity (IEEE-TAS), as a proceedings paper for a contributed talk at the 2012 Applied Superconductivity Conference, Portland, OR

A precise measurement of the neutron decay $\beta$-asymmetry $A_0$ has been carried out using polarized ultracold neutrons (UCN) from the pulsed spallation UCN source at the Los Alamos Neutron Science Center (LANSCE). Combining data obtained in 2008 and 2009, we report $A_0 = -0.11966 \pm 0.00089_{-0.00140}^{+0.00123}$, from which we determine the ratio of the axial-vector to vector weak coupling of the nucleon $g_A/g_V = -1.27590_{-0.00445}^{+0.00409}$., Comment: 5 pages, 2 figures