Gabriel LT, Bianchi RF, Bernardes AT. Mechanical Property Assessment of Interlocking Plastic Pavers Manufactured from Electronic Industry Waste in Brazil. Recycling [Internet]. 2021;6 (1) :15. Publisher's Version
Sousa L, Azevedo ML\'ıza, Rocha D, Andrade Â, Amparo T, dos Santos O, Seibert J\'ına, Pereira L, Vieira P, Carneiro C, et al. Trypanocidal Activity and Increased Solubility of Benznidazole Incorporated in PEG 4000 and Its Derivatives. J. Braz. Chem. Soc. [Internet]. 2021. Publisher's Version
Velten H. Matéria escura e as estruturas cósmicas. Cadernos de Astronomia [Internet]. 2021;2 (1) :58. Publisher's Version
Velten H, Caramês TRP. To conserve, or not to conserve: A review of nonconservative theories of gravity. Universe. 2021;7 (2) :38.
Fabris JC, Gomes T, Toniato JD, Velten H. Newtonian-like gravity with variable G. Eur. Phys. J. Plus [Internet]. 2021;136 (2). Publisher's Version
Ribeiro LC, Bernardes AT. Estimate of underreporting of COVID-19 in Brazil by Acute Respiratory Syndrome hospitalization reports. Notas Técnicas Cedeplar-UFMG [Internet]. 2020;xx (xx) :xx. Publisher's VersionAbstract
The number of COVID-19 infected people in each country is a crucial factor to determine public policies. It guides the governments to strengthen movement restrictions of people or to relieve it. The number of infected people is very important to forecast the needs of the health systems, which are collapsing in many countries. Thus, underreporting of infected people is a huge problem, since authorities do not know the real problem and act in darkness. In the present work, we discuss this subject for the Brazilian case. We take the time series of acute respiratory syndromes reported in the health public system in the last ten years and estimated the number for March/20 when the COVID-19 appeared in Brazil. Our results show a 7.7:1 rate of underreporting, meaning that the real cases in Brazil should be, at least, seven times the publicized number.
Andrade MV, Noronha K, Turra CM, Guedes G, Cimini FANDR, Costa L, Bernardes AT, et. al. Os primeiros 80 dias da pandemia da COVID-19 em Belo Horizonte: da contenção à flexibilização. Nova Economia [Internet]. 2020;30 (0103-6351) :701-737. Publisher's VersionAbstract
Este artigo examina o contexto e as implicações da pandemia por Covid-19 na cidade de Belo Horizonte (BH) nos primeiros 80 dias da doença. Utilizamos um recorte analítico descritivo para mensurar a evolução dos casos, o excesso de óbitos, a taxa de transmissibilidade do vírus e a pressão da doença sobre o sistema de saúde de BH e região, através da taxa de ocupação hospitalar nos leitos públicos. Além disso, identificamos as principais políticas de contenção adotadas pelas autoridades locais, bem como as implicações da redução do distanciamento social. Nossos resultados demonstram que o Sistema Único de Saúde (SUS), bem gerido, é fundamental para o enfrentamento da pandemia e a mitigação de suas consequências para a população. O processo de flexibilização que se inicia tem imposto novos desafios que requererão monitoramento atento das autoridades e da sociedade.
Alencar AB, de Oliveira A, Chacham H. Crystal reorientation and plastic deformation of single-layer MoS2 and MoSe2 under uniaxial stress. Journal of Physics: Condensed Matter [Internet]. 2020. Publisher's VersionAbstract
We investigate theoretically, through of first-principles calculations, the effect of the application of large in-plane uniaxial stress on single-layer of MoS2, MoSe2, and MoSSe alloys. For stress applied along the zigzag direction, we predict an anomalous behavior near the point fracture. This behavior is characterized by the reorientation of the MoS2 structure along the applied stress from zigzag to armchair due to the formation of transient square-lattice regions in the crystal, with an apparent (although not real) crystal rotation of 30 degrees. After reorientation, a large plastic deformation √3-1 remains after the stress is removed. This behavior is also observed in MoSe2 and in MoSSe alloys. This phenomenon is observed both in stress-constrained geometry optimizations and in ab initio molecular dynamics simulations at finite temperature and applied stress.
Velten H, Dito G. Post-Editorial of the Special Issue “Estate Quantistica Conference—Recent Developments in Gravity, Cosmology, and Mathematical Physics”. Universe [Internet]. 2020;6 (12) :240. Publisher's Version
de Santos ABS, Manfredi AM, Salla CAM, Farias G, Girotto E, Eccher J, Westphal E, Curcio SF, Cazati T, Malvestiti I, et al. Highly luminescent liquid crystals by connecting 1,3,4-oxadiazole with thiazolo[5,4-d]thiazole units. Journal of Molecular Liquids [Internet]. 2020 :114887. Publisher's VersionAbstract
The direct bonding between a thiazolo[5,4-d]thiazole and two 1,3,4-oxadiazole units allowed us to create a new and versatile rigid core for luminescent liquid crystal, which showed interesting and variable mesomorphic and photophysical properties. From the 5-bis(5-phenyl-1,3,4-oxadiazol-2-yl)thiazolo[5,4-d]thiazole new core, three molecules with different number of alkoxy chains were synthesized and had their properties correlated with the molecular structure. The molecule with two chains showed a smectic C mesophase, while the mesogens with four and six chains presented hexagonal columnar mesomorphism, which was confirmed by POM and XRD measurements. In addition, the molecule with six chains presented liquid crystalline behavior close to room temperature. In solution, the molecules presented strong photoluminescence ranging from blue to yellow, with quantum yields higher than 0.6. Excited state lifetimes allowed to correlate the fluorescence component associated to the different emitting species to the molecular organization in spin coated films. The molecular energy levels, together with thermal stability and possible charge carrier transport due to molecular packing, suggest that these molecules are promising for optoelectronic applications. Overall, this work contributes to the development of the use of thiazolo[5,4-d]thiazole in liquid crystals, demonstrating its great efficiency and versatility.
Batista RJC, Dias RF, Barboza APM, de Oliveira AB, Manhabosco TM, Gomes-Silva TR, Gadellha AC, Rabelo C, Cançado LGL, Jorio A, et al. Nanomechanics of few-layer materials: do individual layers slide upon folding?. Beilstein J. Nanotechnol. 2020;11 :1801–1808.
Diniz MO, Coelho RS, Bianchi RF, Guerra EM. Electrical Impedance of V 2 O 5/POMA Hybrid Film Deposited by Casting for Application in Ammonia Gas Sensor. Journal of Electronic Materials. 2020 :1–6.
Martins LGP, Silva DL, Smith JS, Lu A-Y, Su C, Hempel M, Occhialini C, Ji X, Pablo R, Alencar RS, et al. Hard, transparent, sp3-containing 2D phase formed from few-layer graphene under compression. Carbon [Internet]. 2020. Publisher's VersionAbstract
Despite several theoretically proposed two-dimensional (2D) diamond structures, experimental efforts to obtain such structures are in initial stage. Recent high-pressure experiments provided significant advancements in the field, however, expected properties of a 2D-like diamond such as sp3 content, transparency and hardness, have not been observed together in a compressed graphene system. Here, we compress few-layer graphene samples on SiO2/Si substrate in water and provide experimental evidence for the formation of a quenchable hard, transparent, sp3-containing 2D phase. Our Raman spectroscopy data indicates phase transition and a surprisingly similar critical pressure for two-, five-layer graphene and graphite in the 4-6 GPa range, as evidenced by changes in several Raman features, combined with a lack of evidence of significant pressure gradients or local non-hydrostatic stress components of the pressure medium up to ≈ 8 GPa. The new phase is transparent and hard, as evidenced from indentation marks on the SiO2 substrate, a material considerably harder than graphene systems. Furthermore, we report the lowest critical pressure (≈ 4 GPa) in graphite, which we attribute to the role of water in facilitating the phase transition. Theoretical calculations and experimental data indicate a novel, surface-to-bulk phase transition mechanism that gives hint of diamondene formation.
Farias G, Salla CAM, da Silva Heying R, Bortoluzzi AJ, Curcio S, Cazati T, dos Santos PL, Monkman AP, de Souza B, BECHTOLD IVANH. Reducing Lifetime in Cu(I) Complexes with Thermally Activated Delayed Fluorescence and Phosphorescence promoted by Chalcogenolate-Diimine Ligand. J. Mater. Chem. C [Internet]. 2020 :-. Publisher's VersionAbstract
Luminescent copper(I) complexes have drawn attention due to their promising performance as alternative optoelectronic materials to the well-known heavy transition metals complexes. Herein, we report the synthesis of six luminescent Cu(I) complexes with phosphines and 1,10-phenanthroline-derived ligands with thiadiazole and selenodiazole groups in order to evaluate the effect of heavy atom on their photophysical properties. Steady-state and time-resolved spectroscopy confirmed delayed fluorescence emission via a thermally activated delayed fluorescence mechanism in all cases. The experimental spectroscopic data was analyzed with detailed quantum-chemical calculations. Interestingly, these complexes did not show the expected “heavy atom effect”, that enhances the spin-orbit coupling matrix elements, but nevertheless the addition of the heavier chalcogens contributed to reduce the photoluminescence lifetime to roughly 800 ns, which is the lowest reported so far for such TADF materials.
dos Teixeira AR, Teixeira RR, Ribeiro IML, Pereira WL, Manhabosco TM, de Brito ACF, Oliveira LAM, de Oliveira K, Nogueira PC. Association of electroanalytical and spectrophotometric methods to evaluate the antioxidant activity of isobenzofuranone in primary cultures of hippocampal neurons. Toxicology in Vitro [Internet]. 2020 :104970. Publisher's VersionAbstract
The isobenzofuran-1(3H)-ones (phthalides) exhibit various biological activities, including antioxidant activity on reactive oxygen species (ROS). An excess of ROS that cannot be naturally contained by cellular enzymatic systems is called redox imbalance, which damage cell membranes, proteins, and DNA, thereby possibly triggering neuronal death in several neurodegenerative diseases. Considering our ongoing efforts to find useful compounds to control redox imbalance, herein we evaluated the antioxidant activity of two phtalides (compounds 3 and 4), using primary cultures of hippocampal neurons. Spectrophotometric assays showed that compound 3 significantly reduced (p ≤ 0.05) ROS levels and lipid peroxidation compared to the control treatment, while compound 4 was unable at any of the tested concentrations. Despite their structural similarity, these compounds behave differently in the intracellular environment, which was reliably corroborated by the determination of oxidation potentials via cyclic voltammetry. It was demonstrated that compound 3 presents a lower oxidation potential. The combination of the mentioned methods allowed us to find a strong correlation between the chemical structure of compounds and their biological effects. Taking together, the results indicate that compound 3 presents desirable characteristics to act as a candidate pharmacological agent for use in the prevention and treatment of neurodegenerative diseases.
Paez EBA, Curcio S, Neme N, Matos M, Correa RS, Pereira FJ, Hilário FF, Cazati T, Taylor JG. Synthesis, Photophysical and Electrochemical Properties of Novel and Highly Fluorescent Difluoroboron Flavanone β-Diketonate Complexes. New J. Chem. [Internet]. 2020 :-. Publisher's VersionAbstract
Difluoroboron β-diketonates complexes are highly luminescent with extensive properties such as their fluorescence both in solution and in solid state and their high molar extinction coefficients. Due to their rich optical properties, these compounds have been studied for their applications in organic electronics such as in self-assembly and applications in biosensors, bio-imaging and optoelectronic devices. The easy and fast synthesis of difluoroboron β-diketonate (BF2dbm) complexes makes their applications even more attractive. Although many different types of difluoroboron β-diketonates complexes have been studied, the cyclic flavanone analogues of these compounds have never been reported in the literature. Therefore, the present work aims to synthesize difluouroboron flavanone β-diketonate complexes, study their photophysical and electrochemical properties and assess their suitability for applications in optoelectronic devices. The synthesis was based on a Baker–Venkataraman reaction which initially provided substituted diketones, which were subsequently reacted with aldehydes to afford the proposed flavanones. The complexation was achieved by reacting flavanones and BF3. Et2O and in total 9 novel compounds were obtained. A representative difluoroboron flavanone complex was subjected to single crystal X-ray diffraction to unequivocally confirm the chemical structure. A stability study indicated only partial degradation of these compounds over a few days in a protic solvent at elevated temperatures. Photophysical studies revealed that the substituent groups and the solvent media significantly influence the electrochemical and photophysical properties of the final compounds, especially the molar absorption coefficient, fluorescence quantum yields, and the band gap. Moreover, the compounds exhibited a single excited-state lifetime in all studied solvent. Computational studies were employed to evaluate ground and excited states properties and carry out DFT and TDDFT level analysis. These studies clarify the role of each state in the experimental absorption spectra as well as the effect of the solvent.
Velten H. Matéria escura, energia escura e a busca por uma nova teoria para a gravitação. Cadernos de Astronomia [Internet]. 2020;1 (1) :40-51. Publisher's Version
Pinheiro CFS, Castro e Silva A, Velten H. Astrobiologia: como modelar o crescimento de organismos na Terra e em exoplanetas. Cadernos de Astronomia [Internet]. 2020;1 (1) :116-122. Publisher's Version
Nascimento LÃ\textordmasculinebia G, Lopes SA, Teodolino ABL, Novack KÃ!`tia M, Barboza APM, Neves BRA, Azevedo MLS, Sousa LRD, M. R. dos Santos V. Novel PEG 4000 derivatives and its use in controlled release of drug indomethacin. QuÃ\-mica Nova [Internet]. 2020;43 :685 - 691. Publisher's Version
Zimdahl W, Fabris JC, Velten H, Herrera R. On (non-)dynamical dark energy. Physics of the Dark Universe [Internet]. 2020;30 :100681. Publisher's VersionAbstract
The current Universe is composed by a mixture of relativistic species, baryonic matter, dark matter and dark energy which evolve in a non-trivial way at perturbative level. An advanced description of the cosmological dynamics should include non-standard features beyond the simplistic approach idealized by the standard cosmology in which cosmic components do not interact, are adiabatic and dissipationless. We promote a full perturbative analysis of linear scalar perturbations of a non-interacting cosmological model containing baryons, dark matter (both pressureless) and a scalar field allowing for the presence of relative entropic perturbations between the three fluids. Assuming an effective scalar-field sound speed equal to one and neglecting anisotropic stresses we establish a new set of equations for the scalar cosmological perturbations. As a consequence of this new approach, we show that tiny departures from a constant scalar field equation of state wS=−1 damage structure formation in a non-acceptable manner. Hence, by strongly constraining wS our results provide compelling evidence in favor of the standard cosmological model and rule out a large class of dynamical dark energy models.