5 research outputs found

    Procesos de magnetización en nanocompuestos granulares de ferrita de NiZn/SiO2 y Fe/SiO2 /

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    Tesis (Doctor en Física)--Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física, 2008.En el presente trabajo, se estudió el comportamiento magnético de diferentes sistemas granulares nanoestructurados y los mecanismos de reversión de la magnetización operantes, relacionándolos con la naturaleza, tamaño medio de grano, relativa abundancia de las fases presentes e interacción entre ellas. Dos conjuntos de sistemas magnéticos granulares fueron sintetizados: uno, formado por partículas nanocristalinas de Ni0,5 Zn0,5 Fe2O4 inmersas en una matriz de SiO2, fabricado mediante la técnica de molienda de alta energía y técnicas de química húmeda, como sol-gel e impregnación, y el otro conjunto, consistente de partículas nanocristalinas de óxidos de hierro inmersas, también, en una matriz de SiO2, pero sintetizado por aleado mecánico.The aim of this work is to study the magnetic behavior of granular nanostructured systems and the involved magnetization reversal mechanisms, relating them with the resulting microstructure. For this purpose, two groups of granular magnetic systems were synthesized. One of them is formed by Ni0,5 Zn0,5 Fe2O4 nanocrystalline particles immersed in a SiO2 matrix synthesized by mechanical alloying and chemical methods, such as sol-gel and wet impregnation techniques. The other group of samples, consisting of nanocrystalline particles of iron oxides also dispersed in a SiO2 matrix, was synthesized by mechanical alloying. From the structural and magnetic characterization, it is found that NiZnFe2O4/SiO2 systems are formed by monodomain particles of NiZn ferrite, having a broad particle-size distribution and a high degree of agglomeration. Such agglomerates of ferrite, strongly coupled by the exchange interaction, are surrounded by the silica phase. The magnetization reversal mechanism operating in these particles is the coherent rotation in all the composites studied, with the exception of those synthesized by the wet impregnation method. In this later case, two reversal modes are acting simultaneously: coherent rotation, for smaller particles, and nucleation and propagation of inverse domains, for those of bigger sizes. For the granular system composed of iron oxides and silica, synthesized by mechanical alloying, the structural and magnetic evolution of the composites during the mechanical milling is studied. The milling process promotes the formation of different iron oxides, resulting in nanocomposites with magnetic properties strongly dependent on the phases formed and their microstructure.Gabriela del Valle Pozo López ; directora Silvia Patricia Silvetti.Fil: Pozo López, Gabriela del Valle.Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina

    Geodivulgar: Geología y Sociedad

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    Memoria final del Proyecto Innova Docencia 2023-23 nº 58. GEODIVULGAR: Geología y SociedadUCMDepto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasFALSEsubmitte

    Global attitudes in the management of acute appendicitis during COVID-19 pandemic: ACIE Appy Study

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    Background: Surgical strategies are being adapted to face the COVID-19 pandemic. Recommendations on the management of acute appendicitis have been based on expert opinion, but very little evidence is available. This study addressed that dearth with a snapshot of worldwide approaches to appendicitis. Methods: The Association of Italian Surgeons in Europe designed an online survey to assess the current attitude of surgeons globally regarding the management of patients with acute appendicitis during the pandemic. Questions were divided into baseline information, hospital organization and screening, personal protective equipment, management and surgical approach, and patient presentation before versus during the pandemic. Results: Of 744 answers, 709 (from 66 countries) were complete and were included in the analysis. Most hospitals were treating both patients with and those without COVID. There was variation in screening indications and modality used, with chest X-ray plus molecular testing (PCR) being the commonest (19\ub78 per cent). Conservative management of complicated and uncomplicated appendicitis was used by 6\ub76 and 2\ub74 per cent respectively before, but 23\ub77 and 5\ub73 per cent, during the pandemic (both P < 0\ub7001). One-third changed their approach from laparoscopic to open surgery owing to the popular (but evidence-lacking) advice from expert groups during the initial phase of the pandemic. No agreement on how to filter surgical smoke plume during laparoscopy was identified. There was an overall reduction in the number of patients admitted with appendicitis and one-third felt that patients who did present had more severe appendicitis than they usually observe. Conclusion: Conservative management of mild appendicitis has been possible during the pandemic. The fact that some surgeons switched to open appendicectomy may reflect the poor guidelines that emanated in the early phase of SARS-CoV-2

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

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    © 2022 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 licenseBackground: 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. Funding: National Institute for Health and Care Research
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