Análisis comparativo de modelos de reducción de orden para la determinación de tensiones en régimen dinámico de un banco de ensayos

En este trabajo se presenta el análisis dinámico de la estructura de soporte de un banco de ensayos de actuadores aplicables a toberas flexibles. La determinación de las tensiones es realizada a partir del análisis de los desplazamientos finales de la estructura. La precisión con que serán obtenidas las tensiones dependerá de la cantidad de grados de libertad considerados en el análisis siendo obvio que la máxima precisión (desplazamiento exacto) solo se logra al incorporar los infinitos grados de libertad de un sólido continuo. La modelización se realizará a través de la discretización de la estructura en elementos finitos siendo necesario contar con la cantidad de elementos necesarios a fin de capturar el comportamiento deseado. Esto requiere una gran capacidad de cálculo a fin de realizar la integración numérica en un tiempo acotado. Una alternativa a esta situación es implementar una técnica de reducción de orden en el modelo dinámico. Aquí consideramos tres técnicas de reducción de orden y se compararán los resultados obtenidos y su influencia en el comportamiento final del modelo del banco de ensayos. Finalmente se propone el esquema que resulta más adecuado para la simulación numérica del banco de ensayos de actuadores.Publicado en: Mecánica Computacional vol. XXXV, no. 7.Facultad de Ingenierí

Análisis comparativo de modelos de reducción de orden para la determinación de tensiones en régimen dinámico de un banco de ensayos

En este trabajo se presenta el análisis dinámico de la estructura de soporte de un banco de ensayos de actuadores aplicables a toberas flexibles. La determinación de las tensiones es realizada a partir del análisis de los desplazamientos finales de la estructura. La precisión con que serán obtenidas las tensiones dependerá de la cantidad de grados de libertad considerados en el análisis siendo obvio que la máxima precisión (desplazamiento exacto) solo se logra al incorporar los infinitos grados de libertad de un sólido continuo. La modelización se realizará a través de la discretización de la estructura en elementos finitos siendo necesario contar con la cantidad de elementos necesarios a fin de capturar el comportamiento deseado. Esto requiere una gran capacidad de cálculo a fin de realizar la integración numérica en un tiempo acotado. Una alternativa a esta situación es implementar una técnica de reducción de orden en el modelo dinámico. Aquí consideramos tres técnicas de reducción de orden y se compararán los resultados obtenidos y su influencia en el comportamiento final del modelo del banco de ensayos. Finalmente se propone el esquema que resulta más adecuado para la simulación numérica del banco de ensayos de actuadores.Publicado en: Mecánica Computacional vol. XXXV, no. 7.Facultad de Ingenierí

Análisis comparativo de modelos de reducción de orden para la determinación de tensiones en régimen dinámico de un banco de ensayos

En este trabajo se presenta el análisis dinámico de la estructura de soporte de un banco de ensayos de actuadores aplicables a toberas flexibles. La determinación de las tensiones es realizada a partir del análisis de los desplazamientos finales de la estructura. La precisión con que serán obtenidas las tensiones dependerá de la cantidad de grados de libertad considerados en el análisis siendo obvio que la máxima precisión (desplazamiento exacto) solo se logra al incorporar los infinitos grados de libertad de un sólido continuo. La modelización se realizará a través de la discretización de la estructura en elementos finitos siendo necesario contar con la cantidad de elementos necesarios a fin de capturar el comportamiento deseado. Esto requiere una gran capacidad de cálculo a fin de realizar la integración numérica en un tiempo acotado. Una alternativa a esta situación es implementar una técnica de reducción de orden en el modelo dinámico. Aquí consideramos tres técnicas de reducción de orden y se compararán los resultados obtenidos y su influencia en el comportamiento final del modelo del banco de ensayos. Finalmente se propone el esquema que resulta más adecuado para la simulación numérica del banco de ensayos de actuadores.Publicado en: Mecánica Computacional vol. XXXV, no. 7.Facultad de Ingenierí

Análisis de requerimientos y determinación preliminar de la potencia de actuación para el TVC de un vehículo lanzador con tobera flexible

En los vehículos lanzadores se requiere de un sistema de control de dirección del vector de empuje (TVC) que permita desarrollar un vuelo a lo largo de una trayectoria programada, así como también compensar las perturbaciones que se presenten durante la fase propulsiva. Existen distintos mecanismos para lograr este objetivo, siendo uno de los más utilizados el basado en modificar la dirección de la tobera de empuje. En el caso de combustibles sólidos, la tobera incluye una junta flexible conformada mediante la unión de un elastómero con aros de acero que posibilita ajustar la orientación del eje de empuje, mediante un actuador lineal montado de manera conveniente entre la tobera y la estructura del vehículo, el que provoca la deformación elástica de la junta. Se abordará la problemática de utilizar un actuador electromecánico (AEM), basado en tecnología de un motor eléctrico sin escobillas (brushless), para conformar el sistema de control de orientación de una tobera flexible. Dichas toberas imponen fuertes requerimientos operativos a los sistemas de actuación, debido a los elevados valores de rigidez y rozamiento que presentan. En lo metodológico se ha procedido formulando el modelo matemático mecánico, con el que se llevó a cabo la simulación numérica de funcionamiento empleando software especializado de acuerdo a los requerimientos impuestos para determinar a priori las potencias requeridas para los diferentes casos de maniobras planteados. Luego, en las condiciones de peor caso, se pasó a optimizar la relación de transmisión teniendo asimismo en cuenta los requerimientos de respuesta en frecuencia para condiciones de funcionamiento lineal.www.caim2014.unne.edu.arFil: Salomone, Javier E. Centro de Investigaciones Aplicadas. Departamento Sistemas Electromecánicos; Argentina.Fil: Pedroni, Juan P. Centro de Investigaciones Aplicadas. Departamento Sistemas Electromecánicos; Argentina.Fil: Jazni, Jorge E. Centro de Investigaciones Aplicadas. Departamento Sistemas Electromecánicos; Argentina.Fil: Dutto, Esteban A. Centro de Investigaciones Aplicadas. Departamento Sistemas Electromecánicos; Argentina.Fil: Cova, Walter J. D. Centro de Investigaciones Aplicadas. Departamento Sistemas Electromecánicos; Argentina.Fil: Lagier, Santiago. Centro de Investigaciones Aplicadas. Departamento Sistemas Electromecánicos; Argentina.Ingeniería Aeroespacia

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

Mortality and pulmonary complications in patients undergoing surgery with perioperative SARS-CoV-2 infection: an international cohort study

Background: The impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on postoperative recovery needs to be understood to inform clinical decision making during and after the COVID-19 pandemic. This study reports 30-day mortality and pulmonary complication rates in patients with perioperative SARS-CoV-2 infection. Methods: This international, multicentre, cohort study at 235 hospitals in 24 countries included all patients undergoing surgery who had SARS-CoV-2 infection confirmed within 7 days before or 30 days after surgery. The primary outcome measure was 30-day postoperative mortality and was assessed in all enrolled patients. The main secondary outcome measure was pulmonary complications, defined as pneumonia, acute respiratory distress syndrome, or unexpected postoperative ventilation. Findings: This analysis includes 1128 patients who had surgery between Jan 1 and March 31, 2020, of whom 835 (74·0%) had emergency surgery and 280 (24·8%) had elective surgery. SARS-CoV-2 infection was confirmed preoperatively in 294 (26·1%) patients. 30-day mortality was 23·8% (268 of 1128). Pulmonary complications occurred in 577 (51·2%) of 1128 patients; 30-day mortality in these patients was 38·0% (219 of 577), accounting for 81·7% (219 of 268) of all deaths. In adjusted analyses, 30-day mortality was associated with male sex (odds ratio 1·75 [95% CI 1·28–2·40], p\textless0·0001), age 70 years or older versus younger than 70 years (2·30 [1·65–3·22], p\textless0·0001), American Society of Anesthesiologists grades 3–5 versus grades 1–2 (2·35 [1·57–3·53], p\textless0·0001), malignant versus benign or obstetric diagnosis (1·55 [1·01–2·39], p=0·046), emergency versus elective surgery (1·67 [1·06–2·63], p=0·026), and major versus minor surgery (1·52 [1·01–2·31], p=0·047). Interpretation: Postoperative pulmonary complications occur in half of patients with perioperative SARS-CoV-2 infection and are associated with high mortality. Thresholds for surgery during the COVID-19 pandemic should be higher than during normal practice, particularly in men aged 70 years and older. Consideration should be given for postponing non-urgent procedures and promoting non-operative treatment to delay or avoid the need for surgery. Funding: National Institute for Health Research (NIHR), Association of Coloproctology of Great Britain and Ireland, Bowel and Cancer Research, Bowel Disease Research Foundation, Association of Upper Gastrointestinal Surgeons, British Association of Surgical Oncology, British Gynaecological Cancer Society, European Society of Coloproctology, NIHR Academy, Sarcoma UK, Vascular Society for Great Britain and Ireland, and Yorkshire Cancer Research

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

Burnout among surgeons before and during the SARS-CoV-2 pandemic: an international survey

Background: SARS-CoV-2 pandemic has had many significant impacts within the surgical realm, and surgeons have been obligated to reconsider almost every aspect of daily clinical practice. Methods: This is a cross-sectional study reported in compliance with the CHERRIES guidelines and conducted through an online platform from June 14th to July 15th, 2020. The primary outcome was the burden of burnout during the pandemic indicated by the validated Shirom-Melamed Burnout Measure. Results: Nine hundred fifty-four surgeons completed the survey. The median length of practice was 10&nbsp;years; 78.2% included were male with a median age of 37&nbsp;years old, 39.5% were consultants, 68.9% were general surgeons, and 55.7% were affiliated with an academic institution. Overall, there was a significant increase in the mean burnout score during the pandemic; longer years of practice and older age were significantly associated with less burnout. There were significant reductions in the median number of outpatient visits, operated cases, on-call hours, emergency visits, and research work, so, 48.2% of respondents felt that the training resources were insufficient. The majority (81.3%) of respondents reported that their hospitals were included in the management of COVID-19, 66.5% felt their roles had been minimized; 41% were asked to assist in non-surgical medical practices, and 37.6% of respondents were included in COVID-19 management. Conclusions: There was a significant burnout among trainees. Almost all aspects of clinical and research activities were affected with a significant reduction in the volume of research, outpatient clinic visits, surgical procedures, on-call hours, and emergency cases hindering the training. Trial registration: The study was registered on clicaltrials.gov "NCT04433286" on 16/06/2020

Omecamtiv mecarbil in chronic heart failure with reduced ejection fraction, GALACTIC‐HF: baseline characteristics and comparison with contemporary clinical trials

Aims: The safety and efficacy of the novel selective cardiac myosin activator, omecamtiv mecarbil, in patients with heart failure with reduced ejection fraction (HFrEF) is tested in the Global Approach to Lowering Adverse Cardiac outcomes Through Improving Contractility in Heart Failure (GALACTIC‐HF) trial. Here we describe the baseline characteristics of participants in GALACTIC‐HF and how these compare with other contemporary trials. Methods and Results: Adults with established HFrEF, New York Heart Association functional class (NYHA) ≥ II, EF ≤35%, elevated natriuretic peptides and either current hospitalization for HF or history of hospitalization/ emergency department visit for HF within a year were randomized to either placebo or omecamtiv mecarbil (pharmacokinetic‐guided dosing: 25, 37.5 or 50 mg bid). 8256 patients [male (79%), non‐white (22%), mean age 65 years] were enrolled with a mean EF 27%, ischemic etiology in 54%, NYHA II 53% and III/IV 47%, and median NT‐proBNP 1971 pg/mL. HF therapies at baseline were among the most effectively employed in contemporary HF trials. GALACTIC‐HF randomized patients representative of recent HF registries and trials with substantial numbers of patients also having characteristics understudied in previous trials including more from North America (n = 1386), enrolled as inpatients (n = 2084), systolic blood pressure &lt; 100 mmHg (n = 1127), estimated glomerular filtration rate &lt; 30 mL/min/1.73 m2 (n = 528), and treated with sacubitril‐valsartan at baseline (n = 1594). Conclusions: GALACTIC‐HF enrolled a well‐treated, high‐risk population from both inpatient and outpatient settings, which will provide a definitive evaluation of the efficacy and safety of this novel therapy, as well as informing its potential future implementation

Surgical site infection after gastrointestinal surgery in children : an international, multicentre, prospective cohort study

Introduction Surgical site infection (SSI) is one of the most common healthcare-associated infections (HAIs). However, there is a lack of data available about SSI in children worldwide, especially from low-income and middle-income countries. This study aimed to estimate the incidence of SSI in children and associations between SSI and morbidity across human development settings. Methods A multicentre, international, prospective, validated cohort study of children aged under 16 years undergoing clean-contaminated, contaminated or dirty gastrointestinal surgery. Any hospital in the world providing paediatric surgery was eligible to contribute data between January and July 2016. The primary outcome was the incidence of SSI by 30 days. Relationships between explanatory variables and SSI were examined using multilevel logistic regression. Countries were stratified into high development, middle development and low development groups using the United Nations Human Development Index (HDI). Results Of 1159 children across 181 hospitals in 51 countries, 523 (45 center dot 1%) children were from high HDI, 397 (34 center dot 2%) from middle HDI and 239 (20 center dot 6%) from low HDI countries. The 30-day SSI rate was 6.3% (33/523) in high HDI, 12 center dot 8% (51/397) in middle HDI and 24 center dot 7% (59/239) in low HDI countries. SSI was associated with higher incidence of 30-day mortality, intervention, organ-space infection and other HAIs, with the highest rates seen in low HDI countries. Median length of stay in patients who had an SSI was longer (7.0 days), compared with 3.0 days in patients who did not have an SSI. Use of laparoscopy was associated with significantly lower SSI rates, even after accounting for HDI. Conclusion The odds of SSI in children is nearly four times greater in low HDI compared with high HDI countries. Policies to reduce SSI should be prioritised as part of the wider global agenda.Peer reviewe