Controlling the Epitaxial Growth of Bi2Te3, BiTe, and Bi4Te3 Pure Phases by Physical Vapor Transport.

Bi2Te3 is a well-studied material because of its thermoelectric properties and, recently, has also been studied as a topological insulator. However, it is only one of several compounds in the Bi-Te system. This work presents a study of the physical vapor transport growth of Bi-Te material focused on determining the growth conditions required to selectively obtain a desired phase of the Bi-Te system, i.e., Bi2Te3, BiTe, and Bi4Te3. Epitaxial films of these compounds were prepared on sapphire and silicon substrates. The results were verified by X-ray diffraction, Raman spectroscopy, and Rutherford backscattering spectrometry.

Room Temperature Lattice Thermal Conductivity of GeSn Alloys.

CMOS-compatible materials for efficient energy harvesters at temperatures characteristic for on-chip operation and body temperature are the key ingredients for sustainable green computing and ultralow power Internet of Things applications. In this context, the lattice thermal conductivity (κ) of new group IV semiconductors, namely Ge1-xSnx alloys, are investigated. Layers featuring Sn contents up to 14 at.% are epitaxially grown by state-of-the-art chemical-vapor deposition on Ge buffered Si wafers. An abrupt decrease of the lattice thermal conductivity (κ) from 55 W/(m·K) for Ge to 4 W/(m·K) for Ge0.88Sn0.12 alloys is measured electrically by the differential 3ω-method. The thermal conductivity was verified to be independent of the layer thickness for strained relaxed alloys and confirms the Sn dependence observed by optical methods previously. The experimental κ values in conjunction with numerical estimations of the charge transport properties, able to capture the complex physics of this quasi-direct bandgap material system, are used to evaluate the thermoelectric figure of merit ZT for n- and p-type GeSn epitaxial layers. The results highlight the high potential of single-crystal GeSn alloys to achieve similar energy harvest capability as already present in SiGe alloys but in the 20 °C-100 °C temperature range where Si-compatible semiconductors are not available. This opens the possibility of monolithically integrated thermoelectric on the CMOS platform.

Enhancement of the Surface Morphology of (Bi0.4Sb0.6)2Te3 Thin Films by In Situ Thermal Annealing.

The study of the exotic properties of the surface states of topological insulators requires defect-free and smooth surfaces. This work aims to study the enhancement of the surface morphology of optimally doped, high-crystalline (Bi0.4Sb0.6)2Te3 films deposited by molecular beam epitaxy on Al2O3 (001) substrates. Atomic force microscopy shows that by employing an in situ thermal post anneal, the surface roughness is reduced significantly, and transmission electron microscopy reveals that structural defects are diminished substantially. Thence, these films provide a great platform for the research on the thickness-dependent properties of topological insulators.

Isothermal Heteroepitaxy of Ge1-x Sn x Structures for Electronic and Photonic Applications.

Epitaxy of semiconductor-based quantum well structures is a challenging task since it requires precise control of the deposition at the submonolayer scale. In the case of Ge1-x Sn x alloys, the growth is particularly demanding since the lattice strain and the process temperature greatly impact the composition of the epitaxial layers. In this paper, the realization of high-quality pseudomorphic Ge1-x Sn x layers with Sn content ranging from 6 at. % up to 15 at. % using isothermal processes in an industry-compatible reduced-pressure chemical vapor deposition reactor is presented. The epitaxy of Ge1-x Sn x layers has been optimized for a standard process offering a high Sn concentration at a large process window. By varying the N2 carrier gas flow, isothermal heterostructure designs suitable for quantum transport and spintronic devices are obtained.

Revisiting the van der Waals Epitaxy in the Case of (Bi0.4Sb0.6)2Te3 Thin Films on Dissimilar Substrates.

Ultrathin films of the ternary topological insulator (Bi0.4Sb0.6)2Te3 are fabricated by molecular beam epitaxy. Although it is generally assumed that the ternary topological insulator tellurides grow by van der Waals epitaxy, our results show that the influence of the substrate is substantial and governs the formation of defects, mosaicity, and twin domains. For this comparative study, InP (111)A, Al2O3 (001), and SrTiO3 (111) substrates were selected. While the films deposited on lattice-matched InP (111)A show van der Waals epitaxial relations, our results point to a quasi-van der Waals epitaxy for the films grown on substrates with a larger lattice mismatch.

Escala predictiva de los resultados adversos en la hemorragia digestiva alta no varicosa / It not climbs predictiva of the adverse results in the high digestive hemorrhage varicose

Introducción: Existen varios sistemas de puntuación para predecir los resultados adversos en los pacientes con hemorragia digestiva alta no varicosa, pero no se han validado lo suficiente y cada uno pertenece a distintas poblaciones fuentes. Objetivo: Demostrar la utilidad de una escala propuesta para predecir las probabilidades de resangrado, de mortalidad y de necesidad de cirugía en los pacientes con hemorragia digestiva alta no varicosa. Métodos: Se realizó un estudio retrospectivo de una prueba diagnóstica en el hospital de Prenda, Luanda, Angola desde enero del 2021 hasta mayo del 2022. El universo estuvo formado por 93 pacientes atendidos durante ese período con el criterio de inclusión de tener el diagnóstico de hemorragia digestiva alta de origen no varicoso. Resultados: De un total de 93 pacientes se obtuvo como desenlace primario una recurrencia del sangrado de 18 pacientes para un 19,35 por ciento del total, seguido con 12 fallecidos para un 12,90 por ciento del total y cuatro fallecidos para un 4,40 por ciento del total. Los valores predictivos de la escala de forma general fueron, al ser aplicada una sensibilidad de 0,91, la especificidad de un 0,92, el valor predictivo negativo de un 0,95 y el valor predictivo negativo de un 0,86. Conclusiones: La escala propuesta tiene una sensibilidad y especificidad adecuada para predecir, en los pacientes con hemorragia digestiva alta no varicosa, la probabilidad de resangrado, de mortalidad y la necesidad de cirugía(AU)

Introduction: Several scoring systems exist to predict adverse outcomes in patients with nonvariceal upper gastrointestinal bleeding, but they have not been sufficiently validated and each pertains to different source populations. Objective: To demonstrate the usefulness of a proposed scoring scale to predict the probability of rebleeding, mortality, and need for surgery in patients with nonvariceal upper gastrointestinal bleeding. Methods: A retrospective study of a diagnostic test was performed at the hospital of Prenda, Luanda, Angola, from January 2021 to May 2022. The study universe consisted of 93 patients attended during that period, with the inclusion criterion of having a diagnosis of upper gastrointestinal bleeding of nonvariceal origin. Results: From a total of 93 patients, the primary outcome was a recurrence of bleeding in 18 patients, accounting for 19.35 percent of the total; followed by 12 deaths, representing 12.90 percent of the total, and four deaths, accounting for 4.40 percent of the total. After the scale was applied, the following general predictive values were obtained: sensitivity of 0.91, specificity of 0.92, negative predictive value of 0.95 and negative predictive value of 0.86. Conclusions: The proposed scale presents adequate sensitivity and specificity for predicting the probability of fatal rebleeding and the need for surgery in patients with nonvariceal upper gastrointestinal bleeding(AU)

Torsión de tumor ovárico en paciente premenopáusica / Torsion of ovarian tumor in premenopausal patient

La torsión de un tumor ovárico constituye una urgencia ginecológica infrecuente. Es causada por la rotación del órgano afectado sobre su pedículo, lo que restringe su vascularización. Una intervención oportuna evita sus complicaciones. No es frecuente su aparición en tumores de ovario mayores de 15 cm. Se trata de una paciente premenopáusica de 47 años de edad que acude a la sala de emergencia del Centro de Diagnóstico Integral María Eugenia González por presentar dolor en mesogastrio e hipogastrio de elevada intensidad acompañada de vómitos. En el examen físico se constató una marcada distención del abdomen por tumor palpable con límite superior a nivel umbilical. Los estudios de imagen mostraron torsión de tumor quístico de ovario de 32 X 22 cm. Se realizó tratamiento quirúrgico: ooforectomía derecha complementado con apendicectomía profiláctica por invaginación(AU)

Torsion of an ovarian tumor is a rare gynecological emergency. It is caused by rotation of the affected organ on its pedicle, which restricts vascularization. Timely surgery avoids complications. It is rare in over 15mm ovarian tumors. This is a 47 years-old premenopausal patient who went to the emergency service of Maria Eugenia Gonzales comprehensive diagnosis center because she presented with acute pain in the mesogastrium and hypogastrium and vomiting. The physical examination revealed sizeable distention of her abdomen due to palpable tumor with upper limit at umbilical level. Scanning tests showed torsion of 32 x 22cm cystic ovarian tumor. She was operated on by using right oophorectomy supplemented with prophylactic appendicectomy through invagination(AU)