An iterative method for a second order problem with nonlinear two-point boundary conditions.

A semi-linear second order ODE under a nonlinear two-point boundary condition is considered. Under appropriate conditions on the nonlinear term of the equation, we define a two-dimensional shooting argument which allows to obtain solutions for some specific situations by the use of Poincar´e-Miranda’s theorem. Finally, we apply this result combined with the method of upper and lower solutions and develop an iterative sequence that converges to a solution of the problem

An iterative method for a second order problem with nonlinear two-point boundary conditions

A semi-linear second order ODE under a nonlinear two-point boundary condition is considered. Under appropriate conditions on the nonlinear term of the equation, we define a two-dimensional shooting argument which allows to obtain solutions for some specific situations by the use of Poincaré-Miranda?s theorem. Finally, we apply this result combined with the method of upper and lower solutions and develop an iterative sequence that converges to a solution of the problem.Fil: Amster, Pablo Gustavo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Matemática; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigaciones Matemáticas "Luis A. Santaló"; ArgentinaFil: Cárdenas Alzate, Pedro Pablo. Universidad Tecnológica de Pereira; Colombi

Planeamiento de la expansión de redes de transmisión a largo plazo usando una formulación basada en ciclos

Desde que se hicieron las primeras referencias teóricas hasta nuestros dÍas, el problema de planeamiento de la expansión de redes de transmisión de energía eléctrica siempre ha sido un tema de interés de investigación tanto desde el punto de vista de la forma de representar matemáticamente la red de transmisión como de los aspectos que debe considerar el plan de expansión y de los métodos de soluci´on que deben aplicarse para resolver los problemas de optimización resultantes

Planeamiento de la expansión de redes de transmisión a largo plazo usando una formulación basada en ciclos

Desde que se hicieron las primeras referencias teóricas hasta nuestros dÍas, el problema de planeamiento de la expansión de redes de transmisión de energía eléctrica siempre ha sido un tema de interés de investigación tanto desde el punto de vista de la forma de representar matemáticamente la red de transmisión como de los aspectos que debe considerar el plan de expansión y de los métodos de soluci´on que deben aplicarse para resolver los problemas de optimización resultantes

Modificación del juego del Hex y su aplicación en la prueba del teorema del punto fijo de Brouwer

El presente artículo presenta una demostración del teorema del punto fijo de Brouwer utilizando una modificación del juego del Hex o también llamado el juego de Nash. Se explica además de forma general las reglas de dicho juego.The present article presents a demonstration of the Brouwer’s fixed point theorem using a modification of the game of the Hex or also called the game of Nash. One explains in addition to general form the rules of this game

Existencia de solución de un problema de contorno aplicando el método de súper y sub-soluciones

En el presente artículo se muestra un resultado de existencia de solución para un problema de contorno usando el método de super y sub-soluciones. Bajo condiciones apropiadas, se prueba la existencia de solución de un problema periódico utilizando el teorema de punto fijo de Schauder.In this paper we show a result of existence of solution for a boundary problem using the method of upper and lower solutions. Under apropiates conditions, we prove the existence of solutions of the periodic problem using the Schauder’s fixed point theorem

Algunos resultados de operadores lineales continuos

En este artículo se presentan dos resultados interesantes de operadores continuos en un espacio de Hilbert

Nociones de matemáticas financieras

Esta obra es una introducción a la variada problemática de la Matemática Financiera, el cual servirá de ayuda a todo público interesado en dicha disciplina. En el enfoque dado, se encuentran los fundamentos precisos para abordar con propiedad la resolución práctica de problemas de las operaciones financieras, estando al alcance de todos los estudiantes con conocimientos básicos de matemáticas, ya que dichos desarrollos se exponen en un lenguaje sencillo y de fácil comprensión

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030