Pontifícia Universidade Católica do Rio de Janeiro
  • Rio de Janeiro, Rio de Janeiro, Brazil
Recent publications
The localization game is a two player combinatorial game played on a graph G=(V,E). The cops choose a set of vertices S1⊆V with |S1|=k. The robber then chooses a vertex v∈V whose location is hidden from the cops, but the cops learn the graph distance between the current position of the robber and the vertices in S1. If this information is sufficient to locate the robber, the cops win immediately; otherwise the cops choose another set of vertices S2⊆V with |S2|=k, and the robber may move to a neighboring vertex. The new distances to the robber are presented, and if the cops can deduce the new location of the robber based on all information they accumulated thus far, then they win; otherwise, a new round begins. If the robber has a strategy to avoid being captured, then she wins. The localization number is defined to be the smallest integer k so that the cops win the game. In this paper we determine the localization number (up to poly-logarithmic factors) of the random geometric graph G∈G(n,r) slightly above the connectivity threshold.
The viability of epitaxial regrowth of InP to passivate lateral mesa surfaces of lattice-matched InGaAs/InP photodiodes is investigated. The effect of the passivation is quantified via a proposed method that uses multiwavelength photoluminescence to determine the surface recombination velocity (SRV). The effective minority charge lateral diffusion length is also obtained using photocurrent measurements with flood illumination. We propose a methodology where this data can be used together with the SRV to estimate the absorber layer minority charge lifetime. A surface recombination velocity of (3.7±0.1)×104 cms⁻¹ was found for the InGaAs/regrown InP interface, which represents a reduction of 2 orders of magnitude when compared to the value of (6.3±0.1)×106 cms⁻¹ obtained for an unpassivated InGaAs surface.
All tropical savannahs are experiencing extensive transformation and degradation, yet conservation strategies do not adequately address threats to savannahs. Here, using a recently published ecosystem intactness metric, we assess the current condition of tropical savannahs across Earth, finding that <3 % remain highly intact. Moreover, their overall levels of protection are low, and of the protected savannahs, just 4 % can be considered highly intact while the majority (>60 %) are in poor condition. In order to address the clear mismatch between the decline in tropical savannah ecosystems’ condition and the response to manage and conserve them, we reviewed the current drivers that lead to tropical savannah degradation and identified conservation approaches being used to address them. Many successful conservation approaches address multiple drivers of change but are applied across small areas. We argue these approaches have the potential to be up-scaled through integrated land-use planning.
Guanabara Bay (GB) is a highly contaminated estuarine system and an important fishing area in Southeastern Brazil. In this regard, knowledge concerning the association of certain contaminants in seafood to abiotic factors and human health risk assessments is still understudied. Therefore, this study aimed to quantify nine toxic elements in highly consumed crabs, shrimp, and squid, and associate the results with abiotic factors. A human health risk assessment was also performed. Our findings indicate that crabs are the main bioaccumulators. Transparency and depth were noteworthy for all three taxonomic groups. In general, contaminant concentrations were below the limits established by different international agencies, except for As, which was higher than the Brazilian limit (1 mg kg − 1). However, the Hazard Index identified risks to consumer health for the ingestion of seafood. This study emphasizes the importance of jointly evaluating different toxic elements, for a more accurate health risk assessment.
Walter Benjamin’s philosophical statement on the task of the translator, as voiced in his celebrated 1923 homonymous essay, finds echoes in two vibrant and otherwise very diverse contemporary responses to the question of translation. The first is that developed by Canadian writer, essayist, and translator Anne Carson, in her renderings of classical literature, as well as in essays and paratexts dedicated to the issue of translation. The second is to be found in Brazilian anthropologist Eduardo Viveiros de Castro’s account of what he construes as an Amerindian theory of translation. I shall consider how Benjamin’s reflections are modulated in each case, with emphasis on the ways Carson and Viveiros de Castro associate the circumstance of translation with the emergence of what they term, respectively, catastrophe and equivocation. Acts of translation extracted from their writings are then examined and shown to give rise to perplexities that are comparable to the baffled reactions Hölderlin’s translations have sparked among his contemporaries, long before Benjamin set them up as a prototype for the task of the translator. The comparative effort is taken as an occasion to reflect on the moving edges of translation – the shifting nature of the criteria that define its identity.
ABSTRACT Firewood is still a major source of household energy in most parts of the world, including Brazil. This study establishes baseline fuelwood consumption for domestic cooking by rural families in Bahia, Brazil, as part of a socioenvironmental project centered on stove substitution. The project, titled “Fogão do Mar” (Seaside Stove), engaged families in adopting more efficient stoves to replace the traditional open-air, rudimentary models. The study involved household visits and interviews with 103 low-income rural families to estimate firewood consumption for domestic cooking. The results showed that all households have liquid petroleum gas (LPG) stove, but most of the families prefer to use a firewood stove for cooking. The annual per capita consumption of firewood was estimated to be 1,297±952 kg, which is higher than estimate by governmental data (560 kg), as well as other rural regions. Therefore, the consumption of firewood is regionalized. Economic factors are decisive in the choice of fuel for cooking.
The paper studies the electronic current in a one-dimensional lead under the effect of spin–orbit coupling and its injection into a metallic conductor through two contacts, forming a closed loop. When an external potential is applied, the time reversal symmetry is broken and the wave vector k of the circulating electrons that contribute to the current is spin-dependent. As the wave function phase depends upon the vector k, the closed path in the circuit produces spin-dependent current interference. This creates a physical scenario in which a spin-polarized current emerges, even in the absence of external magnetic fields or magnetic materials. It is possible to find points in the system’s parameter space and, depending upon its geometry, the value of the Fermi energy and the spin–orbit intensities, for which the electronic states participating in the current have only one spin, creating a high and totally spin-polarized conductance. For a potential of a few tens of meV, it is possible to obtain a spin-polarized current of the order of μA. The properties of the obtained electronic current qualify the proposed device as a potentially important tool for spintronics applications.
Breast cancer is the most frequent cause of cancer death in women, representing the fifth leading cause of cancer death overall. Therefore, the growing search for the development of new treatments for breast cancer has been developed lately as well as drug delivery systems such as biocompatible metal–organic Frameworks (bio-MOFs). These may be promising and attractive for drug incorporation and release. The present study aims to develop a drug carrier system RCA (bioMOF-100 submitted to the activation process) containing incorporated curcumin (CCM), whose material surface is coated with folic acid molecules (FA) to promote the targeting of drug carrier systems to the tumor region. They were synthesized and characterized using several characterization techniques. The materials were submitted to drug encapsulation tests, whose encapsulation efficiency was 32.80% for CCM@RCA-1D. Using the 1H nuclear magnetic resonance (NMR) spectroscopy technique, it was possible to verify the appearance of signals referring to folic acid, suggesting success in the functionalization of these matrices. In vitro tests such as cell viability and type of cell death were evaluated in both series of compounds (CCM@RCA-1D, CCM@RCA-1D/FA) in breast tumor lines. The results revealed low toxicity of the materials and cell death by late apoptosis. Thus, these results indicate that the matrices studied can be promising carriers in the treatment of breast cancer.
Que papel o fenômeno da tradução criativa, tradução icônica, ou transcriação, pode ter entre diversas formas de crítica? Vamos examinar esta questão no escopo da divisão sugerida por Umberto Eco, e sua relação com a tese de Haroldo de Campos de "tradução como crítica" – "se a tradução é uma forma privilegiada de leitura crítica, será através dela que se poderão conduzir outros poetas, amadores e estudantes de literatura à penetração no âmago do texto artístico, nos seus mecanismos e engrenagens mais íntimos". Exploramos essa tese através da noção operacional do ícone, e de ícone diagramático, desenvolvida por C. S. Peirce, e do exame da transcriação do poema "The Expiration", de John Donne, por Augusto de Campos. Em nossa abordagem, a transcriação é um ícone de relações. Ela revela, através de uma operação tipicamente diagramática, um sistema multinível de restrições. Nossa abordagem sugere uma perspectiva epistêmica para o ícone, desconsiderada por Haroldo, capaz de re-situar sua tese em um cenário teórico ainda inexplorado.
Introduction The acoustic analysis of speech (measurements of the fundamental frequency and formant frequencies) of different vowels produced by speakers with the Angle class II, division 1, malocclusion can provide information about the relationship between articulatory and phonatory mechanisms in this type of maxillomandibular disproportion. Objectives To investigate acoustic measurements related to the fundamental frequency (F0) and formant frequencies (F1 and F2) of the oral vowels of Brazilian Portuguese (BP) produced by male speakers with Angle class II, division 1, malocclusion (study group) and compare with men with Angle class I malocclusion (control group). Methods In total, 60 men (20 with class II, 40 with class I) aged between 18 and 40 years were included in the study. Measurements of F0, F1 and F2 of the seven oral vowels of BP were estimated from the audio samples containing repetitions of carrier sentences. The statistical analysis was performed using the Student t -test and the effect size was calculated. Results Significant differences ( p -values) were detected for F0 values in five vowels ([e], [i], [ᴐ], [o] and [u]), and for F1 in vowels [a] and [ᴐ], with high levels for class II, division 1. Conclusion Statistical differences were found in the F0 measurements with higher values in five of the seven vowels analysed in subjects with Angle class II, division 1. The formant frequencies showed differences only in F1 in two vowels with higher values in the study group. The data suggest that data on voice and speech production must be included in the protocol's assessment of patients with malocclusion.
Introdução: O fechamento das escolas devido às restrições da pandemia da COVID-19 acarretou impactos individuais e sociais cada vez mais relatados. Alunos, pais e professores tiveram consequências associadas ao distanciamento escolar predominantemente negativas, com alguns desfechos positivos, mas ainda não sistematicamente mapeados. Objetivo: Promover uma caracterização dos impactos do fechamento das escolas na aprendizagem, nos desenvolvimentos cognitivo e socioemocional e na saúde mental de crianças, pais e professores, por meio de uma revisão sistemática. Métodos: Buscaram-se abstracts nas bases de dados PubMed, Scopus e PsycINFO com a sintaxe dos construtos “estudantes, pais ou professores”, “desenvolvimento cognitivo, socioecioemocional, saúde mental ou desempenho escolar”, e “COVID-19 e fechamento das escolas” entre 2021 e 2022. Resultados: De 622 estudos iniciais, 86 artigos foram incluídos pós-concordância de 100% entre três juízes. Como principais desfechos relacionados ao fechamento das escolas, crianças e adolescentes demonstraram maiores níveis de ansiedade, hiperatividade e desatenção, prejuízos na cognição geral, desenvolvimento motor e quedas significativas de prontidão e de desempenho escolar. Pais apresentaram um aumento em níveis de depressão, ideação suicida, ansiedade e estresse, enquanto professores relataram maiores índices de estresse e burnout. Conclusão: Estes achados apontam a necessidade da elaboração de ações privadas e de políticas públicas em prol da redução dos prejuízos decorrentes do fechamento prolongado das escolas. A principal diretriz norteadora de futuras decisões emergenciais é que as escolas sejam as últimas a fecharem e as primeiras a reabrirem, como uma ação neuro e psicoprotetora.
This study proposes two MMSE symbol-level precoding approaches considering a strict per antenna power constraint and PSK modulation for perfect and imperfect channel state information scenarios. The proposed designs are formulated as second-order cone programs, allowing for an optimal solution via the interior point method. Numerical results confirm that, for the scenario with perfect channel state information, the proposed designs outperform the existing techniques in terms of bit-error-rate for low and intermediate signal-to-noise-ratio. Numerical evaluations also confirm the superiority of the proposed robust MMSE design in the presence of channel state information imperfection.
The presence of Hg and the high consumption of fluorescent lamps (FL) have increased environmental concerns. However, other toxic and potentially toxic elements, like rare earth elements (REE), are neglected in FL. The problems FL cause are currently less in focus since they are being replaced with light emitter diodes (LED). However, replacement is lagging mainly in developing countries, which are usually more affected by electronic wastes. Therefore, it can take many years for FL to be completely phased-out and no longer be a matter of environmental concern. It is essential to keep the FL issue under our attention, considering current consumption and disposal scenarios and the lamps' composition, as demonstrated through life cycle assessment (LCA) works. This revision summarizes the information available in the literature, focusing on 2010 to 2020, on the current scenario of FL regarding its replacement, LCA, contamination risks, disposal, and recycling, highlighting the areas that still require attention. The Hg in lamps can reach the order of mg per lamp. However, Cd, As, Pb, and other potentially toxic metals are also found in FL. In fact, REE have high concentrations in FL, representing more than 23% of the phosphor, and these emergent contaminants are unregulated and have poorly understood environmental effects. Recycling of FL is often low or even inexistent among countries. However, authors have proposed efficient methods for recovering metals (>90% efficiency) and using end-of-life FL in manufacturing new materials. This might be a silver lining to the critical contamination problem arising from FL.
III-V semiconductor materials for high-efficiency multi-junction solar cells are often grown on germanium (Ge) substrates. However, apart from being considered as a rare element, Ge substrates are one of the major cost shares of a III-V multi-junction solar cell. To reduce costs and material consumption, we aim at re-usable porosified Ge substrates. Prior to the growth, the porous layers are subjected to an annealing procedure to close the wafer surface and to form a predetermined breaking area some microns below the surface. Later, the III-V epitaxial layers are mechanically lifted at the porous layer, so the substrate can be reused. Here, we demonstrate the III-V epitaxy material quality by growing Al0.5Ga0.49In0.01As/Ga0.99In0.01As double heterostructures on porous Ge substrates and characterize them in detail to understand how the porous layers affect the structural and opto-electronic properties of the III-V compounds compared to a reference grown on germanium “epi-ready” substrates. We find no significant influence of the porous Ge substrate on the layer’s composition, thickness or roughness. However, cathodoluminescence measurements reveal a defect density of 4.5×10⁵ cm⁻² in comparison with 6.8×10⁴ cm⁻² for the reference case. Those defects were identified as threading dislocations by electron channeling contrast imaging. The lifetime of minority carriers measured by time resolved photoluminescence shows no difference in the low injection regime between both samples either, indicating a high quality opto-electronic material deposited on porous Ge. These first promising results indicate a path for both: reducing costs of III-V multi-junction solar cells and a reduced germanium consumption.
We obtain optimal boundary and global regularity estimates for viscosity solutions of fully nonlinear elliptic equations whose ellipticity degenerates at the critical points of a given solution. We show that any solution is C1,α on the boundary of the domain, for an optimal and explicit α given only in terms of the regularity of the boundary datum and the elliptic degeneracy degree, and independent of the elliptic operator. We also obtain sharp global estimates. We use a different method from all previous results of global nature, which give C1,α regularity only for some small α>0. Our findings are new even for the model equations, involving a degenerate Laplacian.
We report a facile synthesis of p-BiOBr/n-ZnWO4 heterostructures by hydrothermal/precipitation method as an important key player to enhance the photocatalytic degradation of Rhodamine B (RhB) dye and ciprofloxacin antibiotic. The structural and microstructural features confirm that p-BiOBr/n-ZnWO4 heterostructures display a mixed tetragonal/monoclinic phase with the presence of several n-ZnWO4 nanocrystals on the surface of petals of flower-like p-BiOBr microcrystals. X-ray photoluminescence (XPS) analysis of BiOBr exhibits the existence of Bi, O, and Br, whereas BiOBr/ZnWO4-5%, in addition to Bi, O, and Br, consist of signature of Zn and W. UV–Visible spectra of p-BiOBr/n-ZnWO4-5% showed better absorption than p-BiOBr and n-ZnWO4, which advocate an enhanced collection of photons in the heterojunction. An intense photoluminescence emission at room temperature was observed for p-BiOBr microcrystals as compared to p-BiOBr/n-ZnWO4. We observed the best photocatalytic activity for p-BiOBr/n-ZnWO4-2.5% for the degradation of RhB dye at 99.4% in 25 minutes and CIP antibiotic at 58.2% in 170 minutes, which is assigned due to high surface area SBET (13 m²/g), pore size, providing active catalytic sites for bonding chemical and surface interaction and bonding chemical between the bromide/oxides. Finally, we have investigated the use of scavengers for isopropanol, benzoquinone, and sodium azide, which proves that the hydroxyl (•OH) and superoxide (O2′) radicals as the foremost for the chemical reactions to improvement in photocatalytic degradation of RhB dye and antibiotic CIP.
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3,518 members
Rui Haddad
  • Center for Biology and Medical Sciences (CCBM)
Sergey Galkin
  • Department of Mathematics (MAT)
Juliane Callegaro Borsa
  • Department of Psychology (PSI)
Jaqueline de Carvalho Rodrigues
  • Department of Psychology (PSI)
Vladimir N. Zaitsev
  • Department of Chemistry (QUI)
Rua Marquês de São Vicente, 225, Gávea, 22451-900, Rio de Janeiro, Rio de Janeiro, Brazil
Head of institution
Prof. Pe. Josafá Carlos de Siqueira, S.J.
+55 (21) 3527-1001