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1.
Iatreia ; 34(4): 325-334, oct.-dic. 2021. tab, graf
Artigo em Espanhol | LILACS | ID: biblio-1350832

RESUMO

RESUMEN El entendimiento del razonamiento clínico es una necesidad para la investigación, la docencia y la práctica clínica. Los modelos teóricos subyacentes podrían agruparse en tres grandes ejes no excluyentes. El primero es denominado bayesiano informal según su estructura semejante al análisis de probabilidades condicionales. El segundo propone (desde las ciencias cognitivas) un razonamiento dual que es la suma de dos tipos de pensamientos: el tipo 1, rápido e intuitivo y, el tipo 2, hipotético-deductivo. El tercero, el conocimiento intersubjetivo que involucra la interacción del saber del paciente sobre su condición con el del médico, además, de hacer explícito el papel de la emoción. En esta segunda entrega se presenta una revisión narrativa de estas teorías para poder proponer una definición integradora, en la que se presenta al razonamiento clínico como un constructo complejo, iterativo y adaptativo.


SUMMARY Understanding clinical reasoning is a crucial for research, teaching, and daily clinical practice. Theoretical models could be grouped into three main non-exclusive axes. The first describes probability-based thinking, called informal Bayesian, because of its similarity to the conditional probability analysis structure. The second, from the cognitive sciences, describes reasoning as the sum of two types of thinking: type 1 (fast and intuitive) and type 2 (hypothetical-deductive). Finally, the third, intersubjective knowledge, which involves the interaction of the patient's knowledge about his condition with the doctor's knowledge and also makes explicit the role of emotion. In this second part, a narrative review of current theories is presented in order to propose an integrative definition, in which clinical reasoning is presented as a complex, iterative and adaptive construct.


Assuntos
Humanos , Raciocínio Clínico , Processos Mentais , Teoria da Decisão , Viés , Erros Médicos
2.
Int. j. med. surg. sci. (Print) ; 8(2): 1-10, jun. 2021. tab
Artigo em Inglês | LILACS | ID: biblio-1284419

RESUMO

Introduction.Thyroid cancer is currently the first most common cancer in women in Ecuador. This study aimed to assess the changes in clinical presentation and diagnosis of differentiated thyroid cancer at a third level hospital in Quito, Ecuador.Methods and Materials.This is a retrospective case series performed in three consecutive periods from 1990 to 2019 at a tertiary level hospital, in Quito, Ecuador. The clinical records of 875 patients who had been diagnosed and surgically treated for differentiated thyroid cancer were reviewed. Demographic, clinical, imaging, and pathological data were collected and analyzed.Results. Significant trends toward older age, higher educational level, less palpable primary tumors, less palpable neck nodes, less distant metastases, more ultrasound, tomography and cytology exams, smaller primary tumors, more stage I patients, and more histological variant description, were found. Introduction.Thyroid cancer is currently the first most common cancer in women in Ecuador. This study aimed to assess the changes in clinical presentation and diagnosis of differentiated thyroid cancer at a third level hospital in Quito, Ecuador.Methods and Materials.This is a retrospective case series performed in three consecutive periods from 1990 to 2019 at a tertiary level hospital, in Quito, Ecuador. The clinical records of 875 patients who had been diagnosed and surgically treated for differentiated thyroid cancer were reviewed. Demographic, clinical, imaging, and pathological data were collected and analyzed.Results. Significant trends toward older age, higher educational level, less palpable primary tumors, less palpable neck nodes, less distant metastases, more ultrasound, tomography and cytology exams, smaller primary tumors, more stage I patients, and more histological variant description, were found.


Introducción. El cáncer de tiroides es actualmente el cáncer más frecuente en la mujer en Ecuador. El presente estudio ha tenido como objetivo evaluar los cambios en la presentación clínica y el diagnóstico del cáncer diferenciado de tiroides en un hospital de tercer nivel de Quito, Ecuador. Material y Métodos. El presente es un estudio retrospectivo de casos realizado en tres períodos consecutivos desde 1990 a 2019 en un hospital del tercer nivel en Quito, Ecuador. Los expedientes clínicos de 875 pacientes tratados quirúrgicamente por un cáncer diferenciado de tiroides fueron revisados. Los datos demográficos, clínicos, de imagen y patología fueron extraídos y analizados. Resultados. Se encontraron tendencias significativas hacia una edad más avanzada, nivel educativo más alto, menos tumores palpables, menos adenopatías regionales palpables, menos metástasis a distancia, más exámenes de ultrasonido y tomografía, más estudios de citología, más tumores pequeños y pacientes con estadío I y más descripciones de las variantes histológicas. Conclusiones. El cáncer de tiroides no sólo que ha aumentado continuamente en su frecuencia en los años recientes, sino que la presentación clínica, el manejo diagnóstico y terapéutico ha cambiado significativamente en las tres últimas décadas.


Assuntos
Humanos , Masculino , Feminino , Pessoa de Meia-Idade , Neoplasias da Glândula Tireoide/diagnóstico , Neoplasias da Glândula Tireoide/epidemiologia , Fatores de Tempo , Neoplasias da Glândula Tireoide/patologia , Evolução Clínica , Demografia , Estudos Retrospectivos , Autoexame , Equador/epidemiologia , Centros de Atenção Terciária
3.
Rev. colomb. anestesiol ; 49(1): e301, Jan.-Mar. 2021. graf
Artigo em Inglês | LILACS, COLNAL | ID: biblio-1149795

RESUMO

Abstract Complications in airway management remain a common cause of anesthesia-associated mortality. When a patient is considered with anticipated difficult airway, the management depends on several variables, however, at present, the standard of management continues to be the patient awake approach. In scenarios of acute upper airway obstruction, the only way to guarantee adequate ventilation is to obtain a translaryngeal or transtracheal access, for which, it is necessary to use local anesthesia and grade I / II sedation, avoiding loss of spontaneous ventilation. For this purpose, we propose ultrasound-guided superior laryngeal nerve block, in order to standardize an ultrasound landmark that is reproduceable, with a high success rate, which allows limiting complications related to regional anatomic techniques and thus facilitating the securing of the airway in these patients.


Resumen Las complicaciones en el manejo de la vía aérea siguen siendo una causa frecuente de mortalidad relacionada con anestesia. Cuando un paciente se considera con vía aérea difícil anticipada, el manejo depende de diversas variables, sin embargo, en la actualidad, el estándar de manejo sigue siendo el abordaje con paciente despierto. En escenarios de obstrucción aguda de la vía aérea superior, la única forma de garantizar una adecuada ventilación es obtener un acceso translaríngeo o transtraqueal, para lo cual, es necesario el uso de anestesia local y de sedación grado I/II evitando la pérdida de ventilación espontánea. Con este propósito, planteamos el bloqueo del nervio laríngeo superior guiado por ultrasonografía, con el fin de estandarizar una referencia ecográfica reproducible, con alto índice de éxito, la cual permita limitar complicaciones relacionadas con las técnicas regionales anatómicas y así facilitar el aseguramiento de la vía aérea en estos pacientes.


Assuntos
Humanos , Ultrassonografia , Anestesia Local , Nervos Laríngeos , Bloqueio Nervoso , Obstrução das Vias Respiratórias , Anestesiologistas , Intubação
4.
Rev. colomb. anestesiol ; 48(2): 96-99, Jan.-June 2020. tab, graf
Artigo em Inglês | LILACS, COLNAL | ID: biblio-1115563

RESUMO

Abstract Introduction: In the management of the anticipated difficult airway (DA), awake intubation is the strategy of choice. In this context, flexible fibroscopy is the tool most widely used as the first choice. However, there is always the rare case where it may fail. Important findings: Six successful rescue cases using videolaryngoscopy following failed fibroscopy in patients with anticipated DA, and 1 case of rescued extubation of an airway previously secured with fiberoptic bronchoscopy. Conclusion: Videolaringoscopy may be an adequate tool to use as a backup plan for the management of an anticipated DA.


Resumen Introducción: En el manejo de vía aérea difícil anticipada la estrategia de elección es la intubación con el paciente despierto. En este contexto, la fibroscopia flexible es la herramienta más utilizada como plan A; sin embargo, en raras ocasiones puede fallar. Hallazgos importantes: Se presentan seis casos de rescates exitosos con videolaringoscopia luego de fibroscopia fallida en pacientes con vía aérea difícil anticipada, y un caso de rescate de extubación de vía aérea asegurada previamente con fibrobroncoscopio. Conclusión: La videolaringoscopia puede ser una adecuada herramienta como plan B para el manejo de la vía aérea difícil anticipada.


Assuntos
Humanos , Masculino , Feminino , Adulto , Pessoa de Meia-Idade , Manuseio das Vias Aéreas , Falha da Terapia de Resgate , Intubação Intratraqueal , Laringoscopia , Técnicas de Diagnóstico do Sistema Respiratório , Fibras Ópticas
5.
J Phys Chem Lett ; 10(1): 107-112, 2019 Jan 03.
Artigo em Inglês | MEDLINE | ID: mdl-30565946

RESUMO

The properties of crystalline solids can be significantly modified by deliberately introducing point defects. Understanding these effects, however, requires understanding the changes in geometry and electronic structure of the host material. Here we report the effect of forming anion vacancies, via dehydroxylation, in a hexagonal tungsten-bronze-structured iron oxyfluoride, which has potential use as a lithium-ion battery cathode. Our combined pair distribution function and density functional theory analysis indicates that oxygen vacancy formation is accompanied by spontaneous rearrangement of fluorine anions and vacancies, producing dual pyramidal (FeF4)-O-(FeF4) structural units containing 5-fold-coordinated Fe atoms. The addition of lattice oxygen introduces new electronic states above the top of the valence band, with a corresponding reduction in the optical band gap from 4.05 to 2.05 eV. This band gap reduction relative to the FeF3 parent material is correlated with a significant improvement in lithium insertion capability relative to a defect-free compound.

6.
Rev. colomb. anestesiol ; 46(supl.1): 21-25, Dec. 2018. tab, graf
Artigo em Inglês | LILACS, COLNAL | ID: biblio-959823

RESUMO

Abstract Introduction: Airway management in children is one of the challenges faced by physicians in the different care settings. Unlike the adult population, there is no standard-of-reference device for blind intubation in pediatrics. Our group has already conducted a case series study using the I-Gel device for this purpose, but with no acceptable rates of blind intubation. As part of our search for an appropriate device for this purpose, we examined the use of the Air-Q which comes in pediatric sizes but lacks studies for blind intubation in this population. Objective: The main objective of this study was to assess the percentage of successful blind tracheal intubations through the Air-Q supraglottic device. Materials and methods: Prospective sample of 45 pediatric patients weighing between 7 and 50 kg. Besides assessing the percentage of successful blind tracheal intubations, sealing pressures, and fiberoptic visualization through the device were also evaluated and reported, together with the complications associated with the procedure. Results and conclusion: The overall percentage of blind intubation through the Air-Q mask in this study was 55.5%, found to be not acceptable to warrant a recommendation of use for blind intubation; on the other hand, ideal fiberoptic visualiza tion was acceptable, making this method advisable for fiberoptic-guided intubation through the supraglotting device.


Resumen Introducción: El manejo de la vía aérea en el niño hace parte de los desafíos a los cuales debe enfrentarse el médico en los diferentes servicios de atención. A diferencia de la población adulta, en pediatría no existe un dispositivo estándar de referencia para la intubación a ciegas; nuestro grupo ya realizo una serie de casos con el dispositivo I-gel para este propósito, el cual no mostró tasas aceptables de intubación a ciegas; buscando un dispositivo idóneo para este fin, se plantea el dispositivo Air-Q el cual viene en tamaños pediátricos y no tiene estudios en esta población para intubación a ciegas. Objetivo: El objetivo principal de este estudio fue evaluar el porcentaje de éxito en la intubación traqueal a ciegas a través del dispositivo supraglótico Air-Q. Materiales y métodos: Se recogió una muestra prospectiva en una población pediátrica de 45 pacientes con peso entre 7 y 50Kg, además de evaluar el porcentaje de éxito de la intubación traqueal a ciegas, se evaluó la presión de sello, visión fibroscópica a través del dispositivo y se reportaron las complicaciones asociadas al procedimiento. Resultados y conclusiones: El porcentaje global de intuba ción a ciegas a través de la máscara Air-Q en este estudio fue del 55,5%, encontrándolo como un porcentaje no aceptable para recomendar la intubación a ciegas a través de este dispositivo; por otra parte la visión fibroscópica ideal fue aceptable, pudiéndose aconsejar como método para guiar la intubación fibroscópica a través de dispositivo supraglótico.


Assuntos
Humanos
7.
J Chem Phys ; 148(19): 193812, 2018 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-30307207

RESUMO

When an ionic liquid adsorbs onto a porous electrode, its ionic arrangement is deeply modified due to a screening of the Coulombic interactions by the metallic surface and by the confinement imposed upon it by the electrode's morphology. In particular, ions of the same charge can approach at close contact, leading to the formation of a superionic state. The impact of an electrified surface placed between two liquid phases is much less understood. Here we simulate a full supercapacitor made of the 1-butyl-3-methylimidazolium hexafluorophosphate and nanoporous graphene electrodes, with varying distances between the graphene sheets. The electrodes are held at constant potential by allowing the carbon charges to fluctuate. Under strong confinement conditions, we show that ions of the same charge tend to adsorb in front of each other across the graphene plane. These correlations are allowed by the formation of a highly localized image charge on the carbon atoms between the ions. They are suppressed in larger pores, when the liquid adopts a bilayer structure between the graphene sheets. These effects are qualitatively similar to the recent templating effects which have been reported during the growth of nanocrystals on a graphene substrate.

8.
Rev. Fac. Cienc. Méd. Univ. Cuenca ; 36(1): 93-99, Junio 2018. ilus, tab
Artigo em Espanhol | LILACS | ID: biblio-998831

RESUMO

El carcinoma de células de Merkel o también llamado carcinoma neuroendocrino cutáneo es una neoplasia muy rara y agresiva. Se caracteriza por su tendencia a la recurrencia, diseminación ganglionar y metástasis a gran distancia. Se presenta el caso de un paciente masculino de 88 años de edad, con antecedente de carcinoma baso celular en región dorsal, que presenta hace 3 meses una tumoración cutánea en tobillo derecho de gran tamaño, que produce metástasis ganglionar a distancia, el estudio de inmunohistoquímica revela que se trata de un carcinoma neuroendocrino cutáneo, se realiza excéresis del mismo con bordes histológicos negativos, pero a los pocos meses recidiva por lo que se realiza cirugía más profunda y se acompaña de quimioterapia. Se pone énfasis en lo agresivo y tendencia a la recidiva de esta rara enfermedad que podría pasar desapercibida en centros de menor complejidad.


The Merkel cell carcinoma, also known as cutaneous neuroendocrine carcinoma, is a very rare and aggressive neoplasm. It is characterized by its tendency to recurrence, lymph node dissemination and distant metastasis. We present the case of a 88-year-old male patient with a history of basal cell carcinoma in the dorsal region, who presented a large right cutaneous tumor in the right ankle 3 months ago, which produces distant lymph node metastasis. The immunohistochemical study reveals that it is a cutaneous neuroendocrine carcinoma, exeresis is performed with negative histological edges, but after a few months it relapses, so a deeper surgery is performed and it is accompanied by chemotherapy. Emphasis is placed on the aggressiveness and tendency to recurrence of this rare disease that could go unnoticed in centers of less complexity.


Assuntos
Humanos , Masculino , Idoso de 80 Anos ou mais , Neoplasias Cutâneas , Carcinoma de Apêndice Cutâneo , Células de Merkel , Patologia , Recidiva , Metástase Neoplásica
9.
Rev. colomb. anestesiol ; 46(1): 37-41, Jan.-Mar. 2018. tab
Artigo em Inglês | LILACS, COLNAL | ID: biblio-959774

RESUMO

Abstract Introduction: Currently, there are no devices showing an acceptable success rate in blind intubation in pediatrics. Objectives: The purpose of this particular series of cases is to identify the percentage of successful blind intubations using the Igel laryngeal mask in children between 2 and 35 kg of body weight, in addition to evaluating seal pressure, fiber optics vision through the device, and reporting the occurrence of complications. Materials and methods: A prospective case series in pediatrics; patients from 2 to 35 kg. Results: According to our study, the overall percentage of blind intubation was 23%, while the percentages of ideal and low vision to facilitate the insertion of the bronchoscope into the airway, and then inserting a tracheal tube through the fiber optics was 70%. Conclusion: We feel that the supraglottic I-gel is not the appropriate device for blind intubation; however, it is an acceptable recommendation to conduct fiber optics intubation.


Resumen Introducción: No hay un dispositivo en la actualidad que demuestre apropiado porcentaje de éxito de intubación a ciegas en pediatría. Objetivos: El propósito de esta serie de casos es conocer el porcentaje de éxito de intubación a ciegas a través de la máscara laríngea I-gel en niños pesando entre 2 y 35 kilos, además evaluar la presión de sello, la visión fibroscópica a través del dispositivo y reportar la aparición de complicaciones. Materiales y Métodos: Serie prospectiva de casos en pediatría, en pacientes de 2 a 35 kilos. Resultados: En nuestro estudio el porcentaje global de intubación a ciegas fue del 23%, el porcentaje de visión ideal y visión baja, que permiten fácil introducción del broncoscopio en la via aérea y luego a través del fibroscopio introducir un tubo traqueal, fue de un 70%. Conclusiones: Consideramos que el I-gel supraglótico no es un dispositivo adecuado para intubación a ciegas. Sin embargo, tiene un valor aceptable para recomendar realizar intubación fibro-óptica a través del dispositivo supraglótico I-gel. Results: According to our study, the overall percentage of blind intubation was 23%, while the percentages of ideal and low vision to facilitate the insertion of the bronchoscope into the airway, and then inserting a tracheal tube through the fiber optics was 70%. Conclusions: We feel that the supraglottic I-gel is not the appropriate device for blind intubation; however, it is an acceptable recommendation to conduct fiber optics intubation.


Assuntos
Humanos
10.
J Phys Chem Lett ; 8(9): 1925-1931, 2017 May 04.
Artigo em Inglês | MEDLINE | ID: mdl-28403610

RESUMO

Nanoconfinement generally leads to a drastic effect on the physical and chemical properties of ionic liquids. Here we investigate how the electrochemical reactivity in such media may be impacted inside of nanoporous carbon electrodes. To this end, we study a simple electron transfer reaction using molecular dynamics simulations. The electrodes are held at constant electric potential by allowing the atomic charges on the carbon atoms to fluctuate. We show that the Fe3+/Fe2+ couple dissolved in an ionic liquid exhibits a deviation with respect to Marcus theory. This behavior is rationalized by the stabilization of a solvation state of the Fe3+ cation in the disordered nanoporous electrode that is not observed in the bulk. The simulation results are fitted with a recently proposed two solvation state model, which allows us to estimate the effect of such a deviation on the kinetics of electron transfer inside of nanoporous electrodes.

11.
Phys Rev Lett ; 116(13): 135901, 2016 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-27081991

RESUMO

We have performed long time scale molecular dynamics simulations of the cubic and tetragonal phases of the solid lithium-ion electrolyte Li_{7}La_{3}Zr_{2}O_{12} (LLZO), using a first-principles parametrized interatomic potential. Collective lithium transport was analyzed by identifying dynamical excitations: persistent ion displacements over distances comparable to the separation between lithium sites, and stringlike clusters of ions that undergo cooperative motion. We find that dynamical excitations in c-LLZO (cubic) are frequent, with participating lithium numbers following an exponential distribution, mirroring the dynamics of fragile glasses. In contrast, excitations in t-LLZO (tetragonal) are both temporally and spatially sparse, consisting preferentially of highly concerted lithium motion around closed loops. This qualitative difference is explained as a consequence of lithium ordering in t-LLZO and provides a mechanistic basis for the much lower ionic conductivity of t-LLZO compared to c-LLZO.

12.
Rev. colomb. anestesiol ; 43(4): 307-313, Oct.-Dec. 2015. ilus
Artigo em Inglês | LILACS, COLNAL | ID: lil-767539

RESUMO

Ultrasonography as a diagnostic and therapeutic tool has greatly impacted the anesthesiologist's routine in multiple practical applications. However, only recently there have been some reports published in the literature on the use of ultrasonography for the management of the airway in the surgical and ICU patients. Being a portable, easy to use, non-invasive tool that does not require any ionizing energy, ultrasonography becomes highly attractive when the anesthesiologist faces practical issues in a difficult airway. The purpose of this review was precisely to show the potential uses of ultrasonography for difficult airway management, from the literature perspective. There is enough trials-based evidence so far to recommend the use of ultrasonography for the following situations: identification of anatomical airway structures, static detection of a failed or esophageal intubation, dynamic airway measurements, and size determination of endotracheal tubes; identification of predictors of a difficult airway in patients with challenging necks, and trans-tracheal techniques to secure the airway Nevertheless, further studies with strong methodological quality are required to show the potential of ultrasonography to impact the difficult airway management and the morbidity and mortality associated with this condition.


La ecografía como herramienta diagnóstica y terapéutica ha tenido un gran impacto en el quehacer rutinario del anestesiólogo en múltiples áreas de aplicación práctica. Sin embargo, es hasta hace poco en donde han aparecido en la literatura reportes de su uso en situaciones que involucra el manejo de la vía área del paciente en cirugía y unidades de cuidados intensivos. Al ser esta una herramienta portable, fácil de usar, no invasiva y sin necesidad de energía ionizante, la hace altamente atractiva al momento de resolver preguntas prácticas del anestesiólogo que se ve enfrentado a una vía área difícil. Justamente el objetivo de esta revisión fue mostrar desde la literatura cuales son los potenciales usos de los ecografía en el manejo de la vía área. Hasta el momento los estudios muestran suficientes elementos para recomendar su uso en los siguientes situaciones: identificación de estructuras anatómicas en la vía área; detección estática de intubación fallida o esofágica; mediciones dinámicas de la vía área y determinación del tamanño de tubos endotraqueales; predictores de vía área difícil en pacientes con cuello desfavorable; y técnicas transtraqueales para aseguramiento de la vía área. A pesar de ello, aún se requieren mayores estudios con suficiente calidad metodológica en donde se demuestre que el uso de la ecografía si puede llegar a impactar en el manejo de la vía área difícil y en la morbimortalidad generada por esta entidad.


Assuntos
Humanos
13.
Inorg Chem ; 54(19): 9619-25, 2015 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-26378743

RESUMO

Iron fluoride trihydrate can be used to prepare iron hydroxyfluoride with the hexagonal-tungsten-bronze (HTB) type structure, a potential cathode material for batteries. To understand this phase transformation, a structural description of ß-FeF3·3H2O is first performed by means of DFT calculations and Mössbauer spectroscopy. The structure of this compound consists of infinite chains of [FeF6]n and [FeF2(H2O)4]n. The decomposition of FeF3·3H2O induces a collapse and condensation of these chains, which lead to the stabilization, under specific conditions, of a hydroxyfluoride network FeF3-x(OH)x with the HTB structure. The release of H2O and HF was monitored by thermal analysis and physical characterizations during the decomposition of FeF3·3H2O. An average distribution of FeF4(OH)2 distorted octahedra in HTB-FeF3-x(OH)x was obtained subsequent to the thermal hydrolysis/olation of equatorial anionic positions involving F(-) and H2O. This study provides a clear understanding of the structure and thermal properties of FeF3·3H2O, a material that can potentially bridge the recycling of pickling sludge from the steel industry by preparing battery electrodes.

14.
Phys Chem Chem Phys ; 16(18): 8320-31, 2014 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-24658460

RESUMO

Ceria (CeO2) co-doping has been suggested as a means to achieve ionic conductivities that are significantly higher than those in singly doped systems. Rekindled interest in this topic over the last decade has given rise to claims of much improved performance. The present study makes use of computer simulations to investigate the bulk ionic conductivity of rare earth (RE) doped ceria, where RE = Sc, Gd, Sm, Nd and La. The results from the singly doped systems are compared to those from ceria co-doped with Nd/Sm and Sc/La. The pattern that emerges from the conductivity data is consistent with the dominance of local lattice strains from individual defects, rather than the synergistic co-doping effect reported recently, and as a result, no enhancement in the conductivity of co-doped samples is observed.

15.
J Am Chem Soc ; 133(38): 15065-72, 2011 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-21854046

RESUMO

CdO has been studied for decades as a prototypical wide band gap transparent conducting oxide with excellent n-type ability. Despite this, uncertainty remains over the source of conductivity in CdO and over the lack of p-type CdO, despite its valence band maximum (VBM) being high with respect to other wide band gap oxides. In this article, we use screened hybrid DFT to study intrinsic defects and hydrogen impurities in CdO and identify for the first time the source of charge carriers in this system. We explain why the oxygen vacancy in CdO acts as a shallow donor and does not display negative-U behavior similar to all other wide band gap n-type oxides. We also demonstrate that p-type CdO is not achievable, as n-type defects dominate under all growth conditions. Lastly, we estimate theoretical doping limits and explain why CdO can be made transparent by a large Moss-Burstein shift caused by suitable n-type doping.

16.
J Phys Condens Matter ; 23(25): 255402, 2011 Jun 29.
Artigo em Inglês | MEDLINE | ID: mdl-21654047

RESUMO

In this paper we present the parameterization of a new interionic potential for stoichiometric, reduced and doped CeO(2). We use a dipole polarizable potential (DIPPIM: the dipole polarizable ion model) and optimize its parameters by fitting them to a series of density functional theory calculations. The resulting potential was tested by calculating a series of fundamental properties for CeO(2) and by comparing them against experimental values. The values for all the calculated properties (thermal and chemical expansion coefficients, lattice parameters, oxygen migration energies, local crystalline structure and elastic constants) are within 10-15% of the experimental ones, an accuracy comparable to that of ab initio calculations. This result suggests the use of this new potential for reliably predicting atomic scale properties of CeO(2) in problems where ab initio calculations are not feasible due to their size limitations.


Assuntos
Cério/química , Teoria Quântica , Elasticidade , Oxirredução , Oxigênio/química , Temperatura
18.
Quito; FCM; 1992. 57 p. ilus, tab.
Monografia em Espanhol | LILACS | ID: lil-213884

RESUMO

Se realiza un estudio prospectivo en 40 pacientes con diagnóstico de colecistolitiasis, en el Servicio de Cirugía General del Hospital Eugenio Espejo, de Quito, Ecuador, durante el período comprendido entre el 1ro de Agosto de 1991 y el 30 de abril de 1992, con el objeto de establecer si la colangiografía transoperatoria debe ser un procedimiento selectivo o rutinario. Los resultados obtenidos muestran diferencias con relación a la presencia de cálculos no sospechados en la vía biliar, entre los pacientes sometidos a colangiografía transoperatoria que tuvieron indicaciones y aquellos sin indicaciones. El análisis estadístico correspondiente reveló que los mismos son significativos. Los datos sugieren, que la colangiografía transoperatoria debe ser realizada sólo de manera selectiva. El método de estudio seleccionado fué optimo y no se encontró ninguna complicación en la realización de las colangiografías, ni en su posterior análisis, de manera que los resultados que se obtuvieron son seguros y confiables. Sería conveniente realizar en el futuro un estudio comparativo y prospectivo entre los diferentes hospitales de Quito.


Assuntos
Humanos , Masculino , Feminino , Colangiografia/estatística & dados numéricos , Colelitíase/diagnóstico , Centro Cirúrgico Hospitalar
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