20 research outputs found

    CMMSE2017: On two classes of fourth- and seventh-order vectorial methods with stable behavior

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    [EN] A family of fourth-order iterative methods without memory, for solving nonlinear systems, and its seventh-order extension, are analyzed. By using complex dynamics tools, their stability and reliability are studied by means of the properties of the rational function obtained when they are applied on quadratic polynomials. The stability of their fixed points, in terms of the value of the parameter, its critical points and their associated parameter planes, etc. give us important information about which members of the family have good properties of stability and whether in any of them appear chaos in the iterative process. The conclusions obtained in this dynamical analysis are used in the numerical section, where an academical problem and also the chemical problem of predicting the diffusion and reaction in a porous catalyst pellet are solved.This research was partially supported by Ministerio de Economia y Competitividad MTM2014-52016-C02-2-P and Generalitat Valenciana PROMETEO/2016/089.Cordero Barbero, A.; Guasp, L.; Torregrosa Sánchez, JR. (2018). CMMSE2017: On two classes of fourth- and seventh-order vectorial methods with stable behavior. Journal of Mathematical Chemistry. 56(7):1902-1923. https://doi.org/10.1007/s10910-017-0814-0S19021923567S. Amat, S. Busquier, Advances in Iterative Methods for Nonlinear Equations (Springer, Berlin, 2016)S. Amat, S. Busquier, S. Plaza, Review of some iterative root-finding methods from a dynamical point of view. Sci. Ser. A Math. Sci. 10, 3–35 (2004)S. Amat, S. Busquier, S. Plaza, A construction of attracting periodic orbits for some classical third-order iterative methods. Comput. Appl. Math. 189, 22–33 (2006)I.K. Argyros, Á.A. Magreñn, On the convergence of an optimal fourth-order family of methods and its dynamics. Appl. Math. Comput. 252, 336–346 (2015)D.K.R. Babajee, A. Cordero, J.R. Torregrosa, Study of multipoint iterative methods through the Cayley quadratic test. Comput. Appl. Math. 291, 358–369 (2016). doi: 10.1016/J.CAM.2014.09.020P. Blanchard, The dynamics of Newton’s method. Proc. Symp. Appl. Math. 49, 139–154 (1994)F.I. Chicharro, A. Cordero, J.R. Torregrosa, Drawing dynamical and parameters planes of iterative families and methods. Sci. World J. 2013, Article ID 780153 (2013)C. Chun, M.Y. Lee, B. Neta, J. Džunić, On optimal fourth-order iterative methods free from second derivative and their dynamics. Appl. Math. Comput. 218, 6427–6438 (2012)A. Cordero, E. Gómez, J.R. Torregrosa, Efficient high-order iterative methods for solving nonlinear systems and their application on heat conduction problems. Complexity 2017, Article ID 6457532 (2017)A. Cordero, J.R. Torregrosa, Variants of Newton’s method using fifth-order quadrature formulas. Appl. Math. Comput. 190, 686–698 (2007)R.L. Devaney, An Introduction to Chaotic Dynamical Systems (Addison-Wesley Publishing Company, Reading, 1989)P.G. Logrado, J.D.M. Vianna, Partitioning technique procedure revisited: formalism and first application to atomic problems. Math. Chem. 22, 107–116 (1997)C.G. Jesudason, I. Numerical nonlinear analysis: differential methods and optimization applied to chemical reaction rate determination. Math. Chem. 49, 1384–1415 (2011)Á.A. Magreñán, Different anomalies in a Jarratt family of iterative root-finding methods. Appl. Math. Comput. 233, 29–38 (2014)M. Mahalakshmi, G. Hariharan, K. Kannan, The wavelet methods to linear and nonlinear reaction-diffusion model arising in mathematical chemistry. Math. Chem. 51(9), 2361–2385 (2013)K. Maleknejad, M. Alizadeh, An efficient numerical scheme for solving Hammerstein integral equation arisen in chemical phenomenon. Proc. Comput. Sci. 3, 361–364 (2011)B. Neta, C. Chun, M. Scott, Basins of attraction for optimal eighth-order methods to find simple roots of nonlinear equations. Appl. Math. Comput. 227, 567–592 (2014)M.S. Petković, B. Neta, L.D. Petković, J. Džunić, Multipoint Methods for Solving Nonlinear Equations (Elsevier, Amsterdam, 2013)R.C. Rach, J.S. Duan, A.M. Wazwaz, Solving coupled Lane–Emden boundary value problems in catalytic diffusion reactions by the Adomian decomposition method. Math. Chem. 52(1), 255–267 (2014)R. Singh, G. Nelakanti, J. Kumar, A new effcient technique for solving two-point boundary value problems for integro-differential equations. Math. Chem. 52, 2030–2051 (2014

    Effects of hospital facilities on patient outcomes after cancer surgery: an international, prospective, observational study

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    Background Early death after cancer surgery is higher in low-income and middle-income countries (LMICs) compared with in high-income countries, yet the impact of facility characteristics on early postoperative outcomes is unknown. The aim of this study was to examine the association between hospital infrastructure, resource availability, and processes on early outcomes after cancer surgery worldwide.Methods A multimethods analysis was performed as part of the GlobalSurg 3 study-a multicentre, international, prospective cohort study of patients who had surgery for breast, colorectal, or gastric cancer. The primary outcomes were 30-day mortality and 30-day major complication rates. Potentially beneficial hospital facilities were identified by variable selection to select those associated with 30-day mortality. Adjusted outcomes were determined using generalised estimating equations to account for patient characteristics and country-income group, with population stratification by hospital.Findings Between April 1, 2018, and April 23, 2019, facility-level data were collected for 9685 patients across 238 hospitals in 66 countries (91 hospitals in 20 high-income countries; 57 hospitals in 19 upper-middle-income countries; and 90 hospitals in 27 low-income to lower-middle-income countries). The availability of five hospital facilities was inversely associated with mortality: ultrasound, CT scanner, critical care unit, opioid analgesia, and oncologist. After adjustment for case-mix and country income group, hospitals with three or fewer of these facilities (62 hospitals, 1294 patients) had higher mortality compared with those with four or five (adjusted odds ratio [OR] 3.85 [95% CI 2.58-5.75]; p<0.0001), with excess mortality predominantly explained by a limited capacity to rescue following the development of major complications (63.0% vs 82.7%; OR 0.35 [0.23-0.53]; p<0.0001). Across LMICs, improvements in hospital facilities would prevent one to three deaths for every 100 patients undergoing surgery for cancer.Interpretation Hospitals with higher levels of infrastructure and resources have better outcomes after cancer surgery, independent of country income. Without urgent strengthening of hospital infrastructure and resources, the reductions in cancer-associated mortality associated with improved access will not be realised

    “Gasto Tributario - Impuestos a la Riqueza”

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    urante el ultimo año en nuestro país se ha debatido profundamente acerca del sistema tributario vigente, uno de los aspectos de mayor relevancia han sido las franquicias o exenciones tributarias, desde distintas miradas políticas y técnicas se pueden observar opiniones que difieren sustancialmente. La razón fundamental que motivó el tema que será desarrollado en este trabajo, es entregar una mirada amplia referente al nivel de análisis que presentan las evaluaciones y mediciones en el tiempo de las políticas tributarias, principalmente relacionada con la exención del impuesto a la renta en el mercado de capitales, desde la formulación de la metodología para medir el gasto tributario y el impacto que tuvo y su focalización por segmento de contribuyentes a beneficiar. La metodología utilizada consistió en recabar antecedentes e informes que abordan la materia, tanto a nivel interno como externo, recogiendo principalmente las conclusiones que se desprenden por expertos y comisiones que han participado en su confección. Los resultados obtenidos son que Chile cuenta con una metodología clara para el cálculo y la medición de los gastos tributarios, pero los datos carecen de calidad para que los resultados sean evaluados y sirvan de base para la toma de decisiones. También se observó que no existe un seguimiento desde los objetivos que se buscaban impulsar a introducir esta franquicia. Las conclusiones principales son que Chile debe mejorar en los datos y estadísticas que obtiene de los contribuyentes para emitir informes a las autoridades que sirvan para la tomas o decisiones o eventuales correcciones de las políticas impulsadas.El presente trabajo es un análisis crítico de la norma del artículo 107 de la Ley de Impuesto a la Renta de Chile (Decreto Ley Nº 824), que establece una franquicia tributaria a la enajenación de valores que cuentan con presencia bursátil, a la luz del principio de legalidad consagrado en la Constitución Política de la República de Chile, y verificar si cumple o no con dicho principio. Así, se logra determinar que la norma en comento vulnera el principio de legalidad al dejar la definición de un elemento del tipo tributario (tatbestand) como lo es la presencia bursátil a una norma infralegal.This paper is a critical analysis of the rule of article 107 of the Chilean Income Tax Law (Law Decree No. 824), which establishes a tax exemption for the transfer of securities that have a stock market presence, in light of the principle of legality enshrined in the Political Constitution of the Republic of Chile, and verify whether or not it complies with said principle. Thus, it is possible to determine that the rule in question violates the principle of legality by leaving the definition of an element of the tax type (tatbestand) such as stock market presence to a non-statutory regulation.Versión original del auto

    Laparoscopic cystogastrostomy

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    Laparoscopic cystogastrostomy

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    Laparoscopic cystogastrostomy

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    Asthma Control: FEV1 or ACT (Asthma Control Test)?.

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