Towards measurement of UHECR with the ARA experiment

The Askaryan Radio Array (ARA) experiment at the South Pole aims to detect GZK (Greisen–Zatsepin–Kuzmin) neutrinos (of energies from some PeV to higher energies) from extra-galactic sources. ARA looks for Askaryan emission in radio-wavelengths (150 to 800 MHz) from showers induced by neutrino-ice molecule collisions in Antarctica. This thesis was aimed at trying to identify the UHECR (Ultra High Energy Cosmic Ray) signal in the ARA stations (or detectors), with each station consisting of radio antennas inside 200 m deep holes in the ice sheet. The CoREAS (CORSIKA-based Radio Emission from Air Showers) simulation was used to simulate radio emissions from cosmic ray air showers and predict voltage signals produced by UHECR in the ARA detectors. UHECR event templates were made for the ARA detectors. These templates were used in a template matching analysis method in order to identify possible UHECR shower candidates in the ARA-2 and ARA-3 "burn'' sample data for years 2013 to 2017 (the 'burn', or 'unblinded' sample data set consists of 10% of the full data set and is made by randomly selecting 1 in every 10 events in each data run with the goal of cut-tuning prior to analysis of the complete data sample)

Radio propagation in non-uniform media

It has been established that, in naturally occurring ice, exotic propagation modes exist for radio signals. An interesting consequence of this is that it seems possible for signals to propagate to the receiver from an area which lies in the expected shadow zone. We present a ray tracing script based on Fermat\u27s principle that has been developed with the aim to model and understand these propagation modes. The results of this script have been found in agreement with an earlier prediction that over-densities are able to guide the ray paths. In addition to the in-ice problem of propagation modes we use this approach to evaluate approximations made in air-shower radio emission simulations and verify if the approximations break down for certain geometries

Propagating Air Shower Radio Signals to In-ice Antennas

In-ice Askaryan radio experiments like ARA, RNO-G, and ARIANNA have deployed radio antennas inside the Greenlandic and Antarctic ice sheets [1–3]. These in-ice radio experiments are looking to measure the flux of cosmogenic and astrophysical neutrinos at even higher energies than IceCube (> 1017 eV). The in-ice radio detectors are designed to record and measure coherent radio Cherenkov emission, known as Askaryan emission, from the particle cascade induced by the neutrino-ice nuclei collision. Radio emissions from particle cascades, dubbed extensive air showers, induced by ultra-high energy cosmic rays interacting in the atmosphere serve as essential backgrounds for Askaryan radio detectors. Arriving with a relatively high flux, cosmic ray particle cascades produce radio signals with many similar features compared to neutrino signals. As such, cosmic rays provide the ideal calibration signal if their signal is understood and can be separated from the neutrino signal. The effort to fully characterize cosmic-ray signals observed by in-ice radio detectors is underway and will be the goal of this work. However, it should be noted that this work will be limited to in-air radio emissions. In contrast, the in-ice emission when the cosmic-ray shower propagates into the ice sheet will be discussed in another work [4, 5]. In this work, cosmic-ray air shower radio emission will be simulated with CoREAS (CORSIKA- based Radio Emission from Air Showers) [6]. CoREAS is a sub-module of the CORSIKA (COsmic Ray SImulations for KAscade) air shower simulation [7]. CoREAS uses the endpoint formalism to calculate the electric field emission from each shower particle (as simulated by CORSIKA) as the shower propagates and makes no assumptions regarding the emission mechanism. However, the CoREAS code has only been designed to work in air using straight-line ray propagation. In reality, air and ice have density-dependent exponential refractive index profiles that cause radiowave rays to curve as they propagate toward an observer. The ray-bending effect is much less pronounced for air than ice since, in polar ice, the refractive index refractive has an exponential profile which has a large gradient in the first 100 − 200 m. Polar ice refractive index changes from 1.35 at the surface to 1.78 within 100 − 200 m, and the sharp change in the refractive index causes the rays to bend significantly near the ice surface

Parallel processing of radio signals and detector arrays in CORSIKA 8

This contribution describes some recent advances in the parallelization of the generation and processing of radio signals emitted by particle showers in CORSIKA 8. CORSIKA 8 is a Monte Carlo simulation framework for modeling ultra-high energy particle cascades in astroparticle physics. The aspects associated with the generation and processing of radio signals in antennas arrays are reviewed, focusing on the key design opportunities and constraints for deployment of multiple threads on such calculations. The audience is also introduced to Gyges, a lightweight, header-only and flexible multithread self-adaptive scheduler written compliant with C++17 and C++20, which is used to distribute and manage the worker computer threads during the parallel calculations. Finally, performance and scalability measurements are provided and the integration into CORSIKA 8 is commented

Antimicrobial resistance among migrants in Europe: a systematic review and meta-analysis

BACKGROUND: Rates of antimicrobial resistance (AMR) are rising globally and there is concern that increased migration is contributing to the burden of antibiotic resistance in Europe. However, the effect of migration on the burden of AMR in Europe has not yet been comprehensively examined. Therefore, we did a systematic review and meta-analysis to identify and synthesise data for AMR carriage or infection in migrants to Europe to examine differences in patterns of AMR across migrant groups and in different settings. METHODS: For this systematic review and meta-analysis, we searched MEDLINE, Embase, PubMed, and Scopus with no language restrictions from Jan 1, 2000, to Jan 18, 2017, for primary data from observational studies reporting antibacterial resistance in common bacterial pathogens among migrants to 21 European Union-15 and European Economic Area countries. To be eligible for inclusion, studies had to report data on carriage or infection with laboratory-confirmed antibiotic-resistant organisms in migrant populations. We extracted data from eligible studies and assessed quality using piloted, standardised forms. We did not examine drug resistance in tuberculosis and excluded articles solely reporting on this parameter. We also excluded articles in which migrant status was determined by ethnicity, country of birth of participants' parents, or was not defined, and articles in which data were not disaggregated by migrant status. Outcomes were carriage of or infection with antibiotic-resistant organisms. We used random-effects models to calculate the pooled prevalence of each outcome. The study protocol is registered with PROSPERO, number CRD42016043681. FINDINGS: We identified 2274 articles, of which 23 observational studies reporting on antibiotic resistance in 2319 migrants were included. The pooled prevalence of any AMR carriage or AMR infection in migrants was 25·4% (95% CI 19·1-31·8; I2 =98%), including meticillin-resistant Staphylococcus aureus (7·8%, 4·8-10·7; I2 =92%) and antibiotic-resistant Gram-negative bacteria (27·2%, 17·6-36·8; I2 =94%). The pooled prevalence of any AMR carriage or infection was higher in refugees and asylum seekers (33·0%, 18·3-47·6; I2 =98%) than in other migrant groups (6·6%, 1·8-11·3; I2 =92%). The pooled prevalence of antibiotic-resistant organisms was slightly higher in high-migrant community settings (33·1%, 11·1-55·1; I2 =96%) than in migrants in hospitals (24·3%, 16·1-32·6; I2 =98%). We did not find evidence of high rates of transmission of AMR from migrant to host populations. INTERPRETATION: Migrants are exposed to conditions favouring the emergence of drug resistance during transit and in host countries in Europe. Increased antibiotic resistance among refugees and asylum seekers and in high-migrant community settings (such as refugee camps and detention facilities) highlights the need for improved living conditions, access to health care, and initiatives to facilitate detection of and appropriate high-quality treatment for antibiotic-resistant infections during transit and in host countries. Protocols for the prevention and control of infection and for antibiotic surveillance need to be integrated in all aspects of health care, which should be accessible for all migrant groups, and should target determinants of AMR before, during, and after migration. FUNDING: UK National Institute for Health Research Imperial Biomedical Research Centre, Imperial College Healthcare Charity, the Wellcome Trust, and UK National Institute for Health Research Health Protection Research Unit in Healthcare-associated Infections and Antimictobial Resistance at Imperial College London

Surgical site infection after gastrointestinal surgery in high-income, middle-income, and low-income countries: a prospective, international, multicentre cohort study

Background: Surgical site infection (SSI) is one of the most common infections associated with health care, but its importance as a global health priority is not fully understood. We quantified the burden of SSI after gastrointestinal surgery in countries in all parts of the world. Methods: This international, prospective, multicentre cohort study included consecutive patients undergoing elective or emergency gastrointestinal resection within 2-week time periods at any health-care facility in any country. Countries with participating centres were stratified into high-income, middle-income, and low-income groups according to the UN's Human Development Index (HDI). Data variables from the GlobalSurg 1 study and other studies that have been found to affect the likelihood of SSI were entered into risk adjustment models. The primary outcome measure was the 30-day SSI incidence (defined by US Centers for Disease Control and Prevention criteria for superficial and deep incisional SSI). Relationships with explanatory variables were examined using Bayesian multilevel logistic regression models. This trial is registered with ClinicalTrials.gov, number NCT02662231. Findings: Between Jan 4, 2016, and July 31, 2016, 13 265 records were submitted for analysis. 12 539 patients from 343 hospitals in 66 countries were included. 7339 (58·5%) patient were from high-HDI countries (193 hospitals in 30 countries), 3918 (31·2%) patients were from middle-HDI countries (82 hospitals in 18 countries), and 1282 (10·2%) patients were from low-HDI countries (68 hospitals in 18 countries). In total, 1538 (12·3%) patients had SSI within 30 days of surgery. The incidence of SSI varied between countries with high (691 [9·4%] of 7339 patients), middle (549 [14·0%] of 3918 patients), and low (298 [23·2%] of 1282) HDI (p < 0·001). The highest SSI incidence in each HDI group was after dirty surgery (102 [17·8%] of 574 patients in high-HDI countries; 74 [31·4%] of 236 patients in middle-HDI countries; 72 [39·8%] of 181 patients in low-HDI countries). Following risk factor adjustment, patients in low-HDI countries were at greatest risk of SSI (adjusted odds ratio 1·60, 95% credible interval 1·05–2·37; p=0·030). 132 (21·6%) of 610 patients with an SSI and a microbiology culture result had an infection that was resistant to the prophylactic antibiotic used. Resistant infections were detected in 49 (16·6%) of 295 patients in high-HDI countries, in 37 (19·8%) of 187 patients in middle-HDI countries, and in 46 (35·9%) of 128 patients in low-HDI countries (p < 0·001). Interpretation: Countries with a low HDI carry a disproportionately greater burden of SSI than countries with a middle or high HDI and might have higher rates of antibiotic resistance. In view of WHO recommendations on SSI prevention that highlight the absence of high-quality interventional research, urgent, pragmatic, randomised trials based in LMICs are needed to assess measures aiming to reduce this preventable complication