Impedance has traditionally been employed in esophageal disease as a means to assess bolus flow and reflux episodes. Recent and ongoing research has provided new and novel applications for this ...technology. Measurement of esophageal mucosal impedance, via either multichannel intraluminal impedance catheters or specially designed endoscopically deployed impedance catheters, provides a marker of mucosal integrity. Mucosal impedance has been shown to segregate gastroesophageal reflux disease (GERD) and eosinophilic esophagitis from non‐GERD controls and may play a role in predicting response to reflux intervention. More data are needed with regard to other esophageal subgroups, outcome studies, and functional disease. Our paper reviews the history of impedance in esophageal disease, the means of assessing baseline and mucosal impedance, data with regard to the newly developed mucosal impedance probes, the clinical utility of mucosal impedance in specific clinical conditions, and limitations in our existing knowledge, along with suggestions for future studies.
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BFBNIB, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
The compact configuration of Phase II of the Murchison Widefield Array (MWA) consists of both a redundant subarray and pseudo-random baselines, offering unique opportunities to perform sky-model and ...redundant interferometric calibration. The highly redundant hexagonal cores give improved power spectrum sensitivity. In this paper, we present the analysis of nearly 40 hr of data targeting one of the MWA's epoch of reionization (EoR) fields observed in 2016. We use both improved analysis techniques presented in Barry et al. and several additional techniques developed for this work, including data quality control methods and interferometric calibration approaches. We show the EoR power spectrum limits at redshift 6.5, 6.8, and 7.1 based on our deep analysis on this 40 hr data set. These limits span a range in k-space of 0.18 h Mpc−1 < k < 1.6 h Mpc−1, with a lowest measurement of Δ2 ≤ 2.39 × 103 mK2 at k = 0.59 h Mpc−1 and z = 6.5.
Malignancy represents substantial morbidity and mortality in patients with primary sclerosing cholangitis (PSC). This subset of patients has been proven to be at increased risk for developing ...cholangiocarcinoma, gallbladder carcinoma and colorectal cancer in those with overlapping inflammatory bowel disease. Herein, we review the prevalence of these malignancies and recommend screening tools and current knowledge to reduce the disease burden in this population. Cholangiocarcinoma is the most dominant malignancy affecting PSC patients, with a lifetime risk ranging from 5% to 20%. We advocate for serial US or MRI/MRCP and CA 19‐9 to screen for cholangiocarcinoma. Gallbladder cancer has a lifetime risk around 2% in this population and we agree with annual imaging for lesions as recommended by national guidelines. Patients with PSC and concomitant IBD are at increased risk of colorectal carcinoma from time of diagnosis and therefore should likely undergo annual surveillance. The low rates of hepatocellular cancer and pancreatic cancer indicate surveillance for these malignancies is less advantageous.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
Eosinophilic esophagitis (EoE) is a clinicopathologic disease characterized by symptoms of esophageal dysfunction and esophageal eosinophilia. In the last decade, there has been a dramatic increase ...in its prevalence for reasons that are not completely understood. The underlying pathophysiology involves an antigen‐mediated TH2 immune response that draws eosinophils to the esophagus, causing mucosal inflammation, esophageal remodeling, and fibrosis. This ultimately leads to esophageal dysfunction that most commonly manifests as dysphagia. In this review, we will discuss updates on key questions regarding the diagnosis and treatment of EoE.
Eosinophilic esophagitis (EoE) is a clinicopathologic disease characterized by symptoms of esophageal dysfunction and esophageal eosinophilia. The underlying pathophysiology involves an antigen‐mediated TH2 immune response that draws eosinophils to the esophagus, causing mucosal inflammation, esophageal remodeling, and fibrosis. This ultimately leads to esophageal dysfunction that most commonly manifests as dysphagia. In this review, we will discuss updates on key questions regarding the diagnosis and treatment of EoE.
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BFBNIB, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
The inductorless piezoelectric transformer (PT)-based resonant converter topology allows all the components between the half-bridge inverter and rectifier in a conventional LCC converter to be ...replaced with a single ceramic component. This offers potential savings in cost, size, and mass. However, zero-voltage switching (ZVS) becomes more difficult to achieve because the MOSFET output capacitances are augmented by the PT input capacitance. This paper presents an analytical model for the ZVS condition in inductorless PT-based converters. Unlike previously reported models, the proposed model is shown to offer a level of accuracy comparable to a SPICE simulation and to correlate well with experimental results. Using a normalization scheme and numerical optimization techniques, the criteria for achieving inductorless ZVS are found in terms of the equivalent circuit components. Both ac-output and dc-output variants are considered, and design charts for ensuring ZVS in five different topologies are presented. The results and design charts are applicable to any type of PT that can be represented by the standard PT equivalent circuit.
We present the results of a coordinated campaign conducted with the Murchison Widefield Array (MWA) to shadow fast radio bursts (FRBs) detected by the Australian Square Kilometre Array Pathfinder ...(ASKAP) at 1.4 GHz, which resulted in simultaneous MWA observations of seven ASKAP FRBs. We de-dispersed the 24 × 1.28 MHz MWA images across the 170-200 MHz band taken at 0.5 s time resolution at the known dispersion measures (DMs) and arrival times of the bursts and searched both within the ASKAP error regions (typically ∼10′ × 10′), and beyond (4° × 4°). We identified no candidates exceeding a 5 threshold at these DMs in the dynamic spectra. These limits are inconsistent with the mean fluence scaling of = −1.8 0.3 ( , where is the observing frequency) that is reported for ASKAP events, most notably for the three high-fluence ( Jy ms) FRBs 171020, 180110, and 180324. Our limits show that pulse broadening alone cannot explain our non-detections, and that there must be a spectral turnover at frequencies above 200 MHz. We discuss and constrain parameters of three remaining plausible spectral break mechanisms: free-free absorption, intrinsic spectral turnover of the radiative processes, and magnification of signals at ASKAP frequencies by caustics or scintillation. If free-free absorption were the cause of the spectral turnover, we constrain the thickness of the absorbing medium in terms of the electron temperature, T, to <0.03 (T/104 K)−1.35 pc for FRB 171020.
Studying the gravitational-wave sky with pulsar timing arrays (PTAs) is a key science goal for the Square Kilometre Array (SKA) and its pathfinder telescopes. With current PTAs reaching ...sub-microsecond timing precision, making accurate measurements of interstellar propagation effects and mitigating them effectively has become increasingly important to realize PTA goals. As these effects are much stronger at longer wavelengths, low-frequency observations are most appealing for characterizing the interstellar medium (ISM) along the sight lines toward PTA pulsars. The Murchison Widefield Array (MWA) and the Engineering Development Array (EDA), which utilizes MWA technologies, present promising opportunities for undertaking such studies, particularly for PTA pulsars located in the southern sky. Such pulsars are also the prime targets for PTA efforts planned with the South African MeerKAT, and eventually with the SKA. In this paper we report on observations of two bright southern millisecond pulsars, PSR J0437−4715 and PSR J2145−0750, made with these facilities; MWA observations sampled multiple frequencies across the 80-250 MHz frequency range, while the EDA provided direct-sampled baseband data to yield a large instantaneous usable bandwidth of ∼200 MHz. Using these exploratory observations, we investigate various aspects relating to pulsar emission and ISM properties, such as spectral evolution of the mean pulse shape, scintillation as a function of frequency, chromaticity in interstellar dispersion, and flux density spectra at low frequencies. Systematic and regular monitoring observations will help ascertain the role of low-frequency measurements in PTA experiments, while simultaneously providing a detailed characterization of the ISM toward the pulsars, which will be useful in devising optimal observing strategies for future PTA experiments.
We examine data from the Murchison Widefield Array (MWA) in the frequency range 72-102 MHz for a field of view that serendipitously contained the interstellar object 'Oumuamua on 2017 November 28. ...Observations took place with a time resolution of 0.5 s and a frequency resolution of 10 kHz. Based on the interesting but highly unlikely suggestion that 'Oumuamua is an interstellar spacecraft, due to some unusual orbital and morphological characteristics, we examine our data for signals that might indicate the presence of intelligent life associated with 'Oumuamua. We searched our radio data for (1) impulsive narrowband signals, (2) persistent narrowband signals, and (3) impulsive broadband signals. We found no such signals with nonterrestrial origins and make estimates of the upper limits on equivalent isotropic radiated power (EIRP) for these three cases of approximately 7 kW, 840 W, and 100 kW, respectively. These transmitter powers are well within the capabilities of human technologies, and are therefore plausible for alien civilizations. While the chances of positive detection in any given search for extraterrestrial intelligence (SETI) experiment are vanishingly small, the characteristics of new generation telescopes such as the MWA (and, in the future, the Square Kilometre Array) make certain classes of SETI experiments easy, or even a trivial by-product of astrophysical observations. This means that the future costs of SETI experiments are very low, allowing large target lists to partially balance the low probability of a positive detection.
Abstract
Recently, low-frequency, broad-band radio emission has been observed accompanying bright meteors by the Long Wavelength Array (LWA). The broad-band spectra between 20 and 60 MHz were ...captured for several events, while the spectral index (dependence of flux density on frequency, with Sν ∝ να) was estimated to be −4 ± 1 during the peak of meteor afterglows. Here we present a survey of meteor emission and other transient events using the Murchison Wide Field Array (MWA) at 72–103 MHz. In our 322 h survey, down to a 5σ detection threshold of 3.5 Jy beam−1, no transient candidates were identified as intrinsic emission from meteors. We derived an upper limit of −3.7 (95 per cent confidence limit) on the spectral index in our frequency range. We also report detections of other transient events, such as reflected FM broadcast signals from small satellites, conclusively demonstrating the ability of the MWA to detect and track space debris on scales as small as 0.1 m in low Earth orbits.
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