On the Initialization of Typical Ignition Models in the Context of Spark-Ignition Devices

Several ignition models have been proposed over the years in order to handle the complex phenomena taking place between the instant a spark is discharged in a combustible mixture and the arising flame becomes self-sustained. Energy stored either in an inductor or a capacitor flows from the primary to the secondary side of a transformer, where voltage becomes high enough to produce the breakdown of the gas. After the conducting channel is generated, energy is transferred either in arc or glow mode, depending on the electrical circuit parameters. Due to the extremely short time and lenght scales involved in the post-breakdown stage, it has become quite standard to employ the simplification of imposing an expanded hot plasma channel, whose thermodynamic state and dimensions depend on a few predominant parameters. As the temperature gradient is initially very high, a heat diffusion equation is normally solved to predict the plasma expansion until the temperature drops below a predefined threshold, such that heat diffusion effects are overcome by the chemistry of the mixture. In this work we assess the appropriateness of the usual approach and compare it to a more recent published alternative, both of which are meticulously analyzed. Main advantages and disadvantages of their utilization are underlined, and the need for a better approach is introduced.Fil: Aranciaga, Joaquín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación En Tecnologías y Ciencias de la Ingeniería. Universidad Nacional del Comahue. Instituto de Investigación En Tecnologías y Ciencias de la Ingeniería; ArgentinaFil: Lopez, Ezequiel Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación En Tecnologías y Ciencias de la Ingeniería. Universidad Nacional del Comahue. Instituto de Investigación En Tecnologías y Ciencias de la Ingeniería; ArgentinaFil: Nigro, Norberto Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones en Métodos Computacionales. Universidad Nacional del Litoral. Centro de Investigaciones en Métodos Computacionales; Argentin

Comparacion entre Valores de Vtec Predichos por el Modelo Nequick2 y los Obtenidos a Partir de Gps sobre Boulder durante muy baja actividad Solar

Una especificación confiable del estado de la ionósfera dada por modelos empíricos es importante para mitigar los efectos que esta zona atmosférica produce sobre las operaciones de los sistemas de posicionamiento y navegación basadas en satélites. Este estudio evalúa la capacidad del modelo NeQuick2 para predecir el contenido electrónico vertical total (VTEC), hasta la altura de los satélites GPS, sobre Boulder (40,00°N, 254,75°E), durante una época de muy baja actividad solar. Para ello se comparan las predicciones del modelo con valores de VTEC obtenidos a partir de señales de satélites GPS, publicados por el National Geophysical Data Center (NGDC) de EEUU. Teniendo en cuenta las incertezas de los valores de GPS VTEC publicados por el NGDC, los resultados muestran que el modelo estudiado, en general, se comporta como un buen predictor del contenido electrónico total en las condiciones solares consideradas

Brain clocks capture diversity and disparities in aging and dementia

Brain clocks, which quantify discrepancies between brain age and chronological age, hold promise for understanding brain health and disease. However, the impact of diversity (including geographical, socioeconomic, sociodemographic, sex and neurodegeneration) on the brain-age gap is unknown. We analyzed datasets from 5,306 participants across 15 countries (7 Latin American and Caribbean countries (LAC) and 8 non-LAC countries). Based on higher-order interactions, we developed a brain-age gap deep learning architecture for functional magnetic resonance imaging (2,953) and electroencephalography (2,353). The datasets comprised healthy controls and individuals with mild cognitive impairment, Alzheimer disease and behavioral variant frontotemporal dementia. LAC models evidenced older brain ages (functional magnetic resonance imaging: mean directional error = 5.60, root mean square error (r.m.s.e.) = 11.91; electroencephalography: mean directional error = 5.34, r.m.s.e. = 9.82) associated with frontoposterior networks compared with non-LAC models. Structural socioeconomic inequality, pollution and health disparities were influential predictors of increased brain-age gaps, especially in LAC (R² = 0.37, F² = 0.59, r.m.s.e. = 6.9). An ascending brain-age gap from healthy controls to mild cognitive impairment to Alzheimer disease was found. In LAC, we observed larger brain-age gaps in females in control and Alzheimer disease groups compared with the respective males. The results were not explained by variations in signal quality, demographics or acquisition methods. These findings provide a quantitative framework capturing the diversity of accelerated brain aging.</p

Brain clocks capture diversity and disparities in aging and dementia across geographically diverse populations

Peer reviewe

Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world

Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection

On post-breakdown initialization for ignition models

An accurate evaluation of the processes taking place from the spark onset until the flame self-propagates in spark ignition internal combustion engines would be very beneficial. It would provide engine designers with more reliable criteria, and this in turn would help lower harmful emissions and achieve improved energy utilization. In order to be computationally affordable, combustion codes contain models which simplify specific tasks. Particularly, the ignition process is very demanding in terms of computational cost, so ignition models are normally resorted to. Their accuracy heavily relies on the knowledge of the physics of the process and their simplifying hypothesis. Currently widely used low-dimensional models are perceived to oversimplify some essential features, perhaps being the most important the role of plasma hydrodynamics, which eventually defines the kernel shape. In this work the effect some fundamental parameters have on the whole process, such as electrode and spark gap dimensions, amount of discharged energy and initial chamber pressure and temperature, is simulated. A qualitative and quantitative analysis allows the assessment of a recently proposed low-dimensional thermodynamic model devised for fast discharges, and to establish its range of validity. Some modifications to this model are introduced in order to improve its predictive capabilities and to extend its range of applicability. Additionally, the effect of a further arc or glow discharge and the influence of electrode configuration asymmetry are simulated, providing a methodology to treat both cases.Fil: Aranciaga, Joaquín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación En Tecnologías y Ciencias de la Ingeniería. Universidad Nacional del Comahue. Instituto de Investigación En Tecnologías y Ciencias de la Ingeniería; ArgentinaFil: Lopez, Ezequiel Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación En Tecnologías y Ciencias de la Ingeniería. Universidad Nacional del Comahue. Instituto de Investigación En Tecnologías y Ciencias de la Ingeniería; ArgentinaFil: Nigro, Norberto Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones en Métodos Computacionales. Universidad Nacional del Litoral. Centro de Investigaciones en Métodos Computacionales; Argentin

On the Initialization of Typical Ignition Models in the Context of Spark-Ignition Devices

Several ignition models have been proposed over the years in order to handle the complex phenomena taking place between the instant a spark is discharged in a combustible mixture and the arising flame becomes self-sustained. Energy stored either in an inductor or a capacitor flows from the primary to the secondary side of a transformer, where voltage becomes high enough to produce the breakdown of the gas. After the conducting channel is generated, energy is transferred either in arc or glow mode, depending on the electrical circuit parameters. Due to the extremely short time and lenght scales involved in the post-breakdown stage, it has become quite standard to employ the simplification of imposing an expanded hot plasma channel, whose thermodynamic state and dimensions depend on a few predominant parameters. As the temperature gradient is initially very high, a heat diffusion equation is normally solved to predict the plasma expansion until the temperature drops below a predefined threshold, such that heat diffusion effects are overcome by the chemistry of the mixture. In this work we assess the appropriateness of the usual approach and compare it to a more recent published alternative, both of which are meticulously analyzed. Main advantages and disadvantages of their utilization are underlined, and the need for a better approach is introduced.Fil: Aranciaga, Joaquín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación En Tecnologías y Ciencias de la Ingeniería. Universidad Nacional del Comahue. Instituto de Investigación En Tecnologías y Ciencias de la Ingeniería; ArgentinaFil: Lopez, Ezequiel Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación En Tecnologías y Ciencias de la Ingeniería. Universidad Nacional del Comahue. Instituto de Investigación En Tecnologías y Ciencias de la Ingeniería; ArgentinaFil: Nigro, Norberto Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones en Métodos Computacionales. Universidad Nacional del Litoral. Centro de Investigaciones en Métodos Computacionales; Argentin

Brain clocks capture diversity and disparities in aging and dementia across geographically diverse populations

Brain clocks, which quantify discrepancies between brain age and chronological age, hold promise for understanding brain health and disease. However, the impact of diversity (including geographical, socioeconomic, sociodemographic, sex and neurodegeneration) on the brain-age gap is unknown. We analyzed datasets from 5,306 participants across 15 countries (7 Latin American and Caribbean countries (LAC) and 8 non-LAC countries). Based on higher-order interactions, we developed a brain-age gap deep learning architecture for functional magnetic resonance imaging (2,953) and electroencephalography (2,353). The datasets comprised healthy controls and individuals with mild cognitive impairment, Alzheimer disease and behavioral variant frontotemporal dementia. LAC models evidenced older brain ages (functional magnetic resonance imaging: mean directional error = 5.60, root mean square error (r.m.s.e.) = 11.91; electroencephalography: mean directional error = 5.34, r.m.s.e. = 9.82) associated with frontoposterior networks compared with non-LAC models. Structural socioeconomic inequality, pollution and health disparities were influential predictors of increased brain-age gaps, especially in LAC (R² = 0.37, F² = 0.59, r.m.s.e. = 6.9). An ascending brain-age gap from healthy controls to mild cognitive impairment to Alzheimer disease was found. In LAC, we observed larger brain-age gaps in females in control and Alzheimer disease groups compared with the respective males. The results were not explained by variations in signal quality, demographics or acquisition methods. These findings provide a quantitative framework capturing the diversity of accelerated brain aging

International Impact of COVID-19 on the Diagnosis of Heart Disease

Background: The coronavirus disease 2019 (COVID-19) pandemic has adversely affected diagnosis and treatment of noncommunicable diseases. Its effects on delivery of diagnostic care for cardiovascular disease, which remains the leading cause of death worldwide, have not been quantified. Objectives: The study sought to assess COVID-19's impact on global cardiovascular diagnostic procedural volumes and safety practices. Methods: The International Atomic Energy Agency conducted a worldwide survey assessing alterations in cardiovascular procedure volumes and safety practices resulting from COVID-19. Noninvasive and invasive cardiac testing volumes were obtained from participating sites for March and April 2020 and compared with those from March 2019. Availability of personal protective equipment and pandemic-related testing practice changes were ascertained. Results: Surveys were submitted from 909 inpatient and outpatient centers performing cardiac diagnostic procedures, in 108 countries. Procedure volumes decreased 42% from March 2019 to March 2020, and 64% from March 2019 to April 2020. Transthoracic echocardiography decreased by 59%, transesophageal echocardiography 76%, and stress tests 78%, which varied between stress modalities. Coronary angiography (invasive or computed tomography) decreased 55% (p &lt; 0.001 for each procedure). In multivariable regression, significantly greater reduction in procedures occurred for centers in countries with lower gross domestic product. Location in a low-income and lower–middle-income country was associated with an additional 22% reduction in cardiac procedures and less availability of personal protective equipment and telehealth. Conclusions: COVID-19 was associated with a significant and abrupt reduction in cardiovascular diagnostic testing across the globe, especially affecting the world's economically challenged. Further study of cardiovascular outcomes and COVID-19–related changes in care delivery is warranted

Reduction of cardiac imaging tests during the COVID-19 pandemic: The case of Italy. Findings from the IAEA Non-invasive Cardiology Protocol Survey on COVID-19 (INCAPS COVID)

Background: In early 2020, COVID-19 massively hit Italy, earlier and harder than any other European country. This caused a series of strict containment measures, aimed at blocking the spread of the pandemic. Healthcare delivery was also affected when resources were diverted towards care of COVID-19 patients, including intensive care wards. Aim of the study: The aim is assessing the impact of COVID-19 on cardiac imaging in Italy, compare to the Rest of Europe (RoE) and the World (RoW). Methods: A global survey was conducted in May–June 2020 worldwide, through a questionnaire distributed online. The survey covered three periods: March and April 2020, and March 2019. Data from 52 Italian centres, a subset of the 909 participating centres from 108 countries, were analyzed. Results: In Italy, volumes decreased by 67% in March 2020, compared to March 2019, as opposed to a significantly lower decrease (p &lt; 0.001) in RoE and RoW (41% and 40%, respectively). A further decrease from March 2020 to April 2020 summed up to 76% for the North, 77% for the Centre and 86% for the South. When compared to the RoE and RoW, this further decrease from March 2020 to April 2020 in Italy was significantly less (p = 0.005), most likely reflecting the earlier effects of the containment measures in Italy, taken earlier than anywhere else in the West. Conclusions: The COVID-19 pandemic massively hit Italy and caused a disruption of healthcare services, including cardiac imaging studies. This raises concern about the medium- and long-term consequences for the high number of patients who were denied timely diagnoses and the subsequent lifesaving therapies and procedures