Electronic and structural distortions in graphene induced by carbon vacancies and boron doping

We present an ab initio study on the structural and electronic distortions of modified graphene by creation of vacancies, inclusion of boron atoms, and the coexistence of both, by means of thermodynamics and band structure calculations. In the case of coexistence of boron atoms and vacancy, the modified graphene presents spin polarization only when B atoms locate far from vacancy. Thus, when a boron atom fills single- and di-vacancies, it suppresses the spin polarization of the charge density. In particular when B atoms fill a di-vacancy a new type of rearrangement occurs, where a stable BC4 unit is formed inducing important out of plane distortions to graphene. All these findings suggest that new chemical modifications to graphene and new type of vacancies can be used for interesting applications such as sensor and chemical labeling.Comment: 22 pages, 9 figures and 3 table

Glomus tumor of digital artery of thumb: case report

We report on a case of glomus tumor in the branch of the radial artery of the right thumb. The tumor had a 4-year clinical history. The patient reported the development of a 2.0-cm tumor in the interdigital region between the first and second fingers of the right hand on the short flexor muscle of thumb. The patient also complained of severe and progressive pain. Tests using bidirectional Doppler and echo-color-Doppler revealed a presumptive diagnosis of arteriovenous malformation based on the turbulence of the flow and absence of stenosis. The tumor was removed by open surgery and sent for histopathological examination, which showed a diagnosis of glomangioma. The present report describes a rare arterial disease causing extreme discomfort to the patient, which may be treated with surgical resection without sequelae.Os autores relatam um caso de tumor glômico em ramo da artéria radial que irriga o polegar direito, com história clínica de 4 meses. O doente referia o aparecimento de tumoração de aproximadamente 2,0 centímetros na região interdigital, entre o primeiro e o segundo quirodactilos da mão direita, sobre o músculo flexor curto do polegar, extremamente dolorosa e com dor em progressão. Os exames com aparelho de Doppler bidirecional e o eco-color-Doppler apresentaram, como diagnóstico presuntivo, malformação arteriovenosa, pelo turbilhonamento do fluxo e ausência de estenoses. A tumoração foi retirada por cirurgia aberta e encaminhada para exame histopatológico, com diagnóstico de glomangioma. Este relato descreve uma doença arterial pouco frequente, que causa extremo desconforto ao seu portador, mas que é solucionada pela exerese cirúrgica, sem sequelas.32032

Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world

Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection

Glomangioma da artéria digital do polegar: relato de um caso

Os autores relatam um caso de tumor glômico em ramo da artéria radial que irriga o polegar direito, com história clínica de 4 meses. O doente referia o aparecimento de tumoração de aproximadamente 2,0 centímetros na região interdigital, entre o primeiro e o segundo quirodactilos da mão direita, sobre o músculo flexor curto do polegar, extremamente dolorosa e com dor em progressão. Os exames com aparelho de Doppler bidirecional e o eco-color-Doppler apresentaram, como diagnóstico presuntivo, malformação arteriovenosa, pelo turbilhonamento do fluxo e ausência de estenoses. A tumoração foi retirada por cirurgia aberta e encaminhada para exame histopatológico, com diagnóstico de glomangioma. Este relato descreve uma doença arterial pouco frequente, que causa extremo desconforto ao seu portador, mas que é solucionada pela exerese cirúrgica, sem sequelas

TiO2(B) and anatase angstrom-scale wires: A theoretical study

In this work, we model TiO2(B) angstrom-scale wires derived from TiO2(B) (001) ultrathin sheets. By means of density functional theory (DFT) calculations, we study their structural, electronic and thermodynamic properties, comparing with anatase angstrom scale wire with z as growing direction, of which there is experimental evidence. We found locally stable structures. TiO2(B) atomic wire oriented along y direction exhibits significantly lower formation energy (0.33 eV) than the other studied systems (1.05 eV for TiO2(B) wire oriented along x- and 0.88 eV for anatase wire oriented along z-direction). Additionally, we present the simulated X-ray powder diffraction diagrams in order to help the experimental identification of this potential titanium dioxide polymorph's nanostructures. These results could be interesting for their potential applications, such as energy storage and photovoltaic applications, and for fundamental studies as well.Fil: Fernández Werner, Luciana. Universidad de la República; UruguayFil: Gonzalez, Estela Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Faccio, Ricardo. Universidad de la República; UruguayFil: Mombrú, Álvaro W.. Universidad de la República; Urugua

Hydrogen Titanate H2TiO3 Nanowires Derived from K2TiO3 as Potential Materials for Solar Cell Applications: A Theoretical Study

One-dimensional systems of titanium dioxide and titanates are interesting for the fundamental study of physical and chemical properties at the nanoscale. In this work we present the electronic structure, mechanical and optical properties of angstrom scale titanate derived nanowires (ASW) by means of density functional theory (DFT) and Density Functional based Tight Binding (DFTB). This one-dimensional H2TiO3 nanostructure is an interesting real material that could serve for understanding, at a fundamental level, the physical properties of TiO5 concatenated polyhedrons derived from hydrogen titanates. The proposed structural model demonstrates to be locally stable according to phonon analysis, and it can be inferred that the one-dimension structure is essentially preserved. The mechanical properties put this nanowire as a flexible material, that could be used in flexible substrates maintaining its electronic properties. Also, the capacity of this system to be sensitized with a catechol dye was explored. For this porpoise, the adsorption of the catechol molecule was tested showing that the most stable interaction corresponds to a dissociative chelate configuration. Finally, it was possible to verify the capability of the sensitized system for injecting electrons from the catechol dye to the nanowire under visible light exposure. Thus, we present these extreme one-dimensional nanostructured materials as candidates for solar cell applications.Fil: Esteves, Martín. Universidad de la República; UruguayFil: Fernández Werner, Luciana. Universidad de la República; UruguayFil: Bechthold, Pablo Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Física del Sur. Universidad Nacional del Sur. Departamento de Física. Instituto de Física del Sur; ArgentinaFil: Faccio, Ricardo. Universidad de la República; UruguayFil: Mombrú, Álvaro W.. Universidad de la República; Urugua

Ultrathin (0 0 1) and (1 0 0) TiO2(B) sheets: surface reactivity and structural properties

B polymorph of titanium dioxide (TiO2(B)) appears as a metastable phase during thermal annealing of low content sodium layered titanate nanostructures obtained via the widely used hydrothermal synthesis. In addition, the computed formation energy for the TiO2(B) (0 0 1) slabs in the order of the one calculated for anatase (1 0 1) which represents one of the most stable TiO2 surfaces. This encourages the study of this polymorph which could gain prominence in TiO2 applications at the nanoscale. In a first instance ultrathin TiO2(B) sheets, parallel to crystallographic planes (0 0 1) and (1 0 0), are investigated and compared to other well know TiO2 polymorphs, such as rutile and anatase surfaces. Then the adsorption of formic acid on (0 0 1) and (1 0 0) – less stable – TiO2(B) dry ultrathin sheets was studied as the first step for further evaluation of TiO2(B) nanostructures for dye sensitized solar cells (DSSC) applications. The results show that the monodentate through the carbonyl group configuration is the most stable for (0 0 1) sheet while bidentate dissociated configuration is the most stable for (1 0 0) sheet being the computed adsorption energies 0.51 eV and 1.49 eV, respectively. The evaluated reactivity of TiO2(B) slabs is comparable with anatase and indicates that it could be a good adsorbent for common dyes used for dye sensitized solar cells purposes.Fil: Fernández Werner, Luciana. Universidad de la República; UruguayFil: Faccio, Ricardo. Universidad de la República; UruguayFil: Juan, Alfredo. Universidad Nacional del Sur. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pardo, Helena. Universidad de la República; UruguayFil: Montenegro, Benjamín. Universidad de la República; UruguayFil: Mombrú, Álvaro W.. Universidad de la República; Urugua