Universidade Federal de Campina Grande (UFCG)
Recent publications
This paper analyzes the influence of anti-aliasing filters (AAFs) on traveling wave (TW)-based fault location (TWFL) methods. To do so, the Alternative Transients Program (ATP) is used to simulate several fault scenarios on a 230 kV/60 Hz test power system, allowing the assessment of AAFs influence when different TW filters and TWFL algorithms are used. The main goal is to clarify how much “villain” are the AAFs for TWFL methods if their cutoff frequencies are varied in noisy environments. By doing so, the most relevant spectrum band for TWFL solutions is investigated, addressing whether the application of AAFs with reduced cutoff frequencies would be critical or not. Although most people may think that the answer to this question is obvious, the obtained results show evidences that some solutions monitor transients within spectrum ranges wider than those they indeed require. Moreover, although AAFs can relevantly influence the performance of TWFL methods, it is proven that the application of AAFs with reduced cutoff frequencies is not necessarily critical, but rather, it depends on the used TW filters and TWFL methods, such that it can be beneficial when electrical noise is present in monitored signals.
Global climate change tends to intensify water unavailability, especially in semi-arid regions, directly impacting agricultural production. Cowpea is one of the crops with great socio-economic importance in the Brazilian semi-arid region, cultivated mainly under rainfed farming and considered moderately tolerant to water restriction. This species has physiological and biochemical mechanisms of adaptation to these stress factors, but there is still no clear vision of how these responses can not only allow survival, but also ensure yield advances in the field. Besides acclimation mechanisms, the exogenous application of abiotic (salicylic acid, silicon, proline, methionine, and potassium nitrate) and biotic (rhizobacteria) elicitors is promising in mitigating the effects of water restriction. The present literature review discusses the acclimation mechanisms of cowpea and some cultivation techniques, especially the application of elicitors, which can contribute to maintaining crop yield under different water scenarios. The application of elicitors is an alternative way to increase the sustainability of production in rainfed farming in semi-arid regions. However, the use of eliciting substances in cowpea still needs to be carefully explored, given the difficulties caused by genotypic and edaphoclimatic variability under field conditions.
We establish the concept of r-almost Yamabe soliton immersed into a Riemannian manifold, which extends in a natural way the notion of almost Yamabe solitons introduced by Barbosa and Ribeiro. In this setting, under suitable hypothesis on the potential and soliton functions, we prove nonexistence and characterization results. Moreover, some examples of these new geometric objects are presented.
Bionanocomposites include matrices and dispersed phases that combine two or more biomolecules on a nano-metric scale to enhance some nanomaterial properties such as biocompatibility and biodegradability. Nowadays, chitosan (CS), a cationic polysaccharide, is one of the most commonly used bioconstituent in the preparation of bionanocomposites with several other materials, such as clay. CS-clay nanocomposites are extensively explored in applications such as drug delivery systems, dressings, food packaging, and contaminant adsorption, due to their improved physicochemical, barrier, and mechanical properties. Recently, the association of organic molecules alongside CS-clay nanocomposites emerged due to the ability of adding new and specific properties for these materials. In this context, we reviewed recent advances on nanohybrid systems composed of CS-clay with organic molecules and discussed their structural interactions, enhanced properties, synthesis method, applications , and toxicological implications. Furthermore, challenges and future perspectives were considered to establish parameters for conducting future research in this field.
In this paper, we obtain a nonsmooth version of the infinite-dimensional Fountain Theorem established by Batkam and Colin (2013). No symmetry condition on the energy functional is needed in our formulation. As an application, we prove the existence of multiple solutions for the following class of elliptic system (S)Δu−u∈[f̲(x,u,v),f¯(x,u,v)]a.e inRN−Δv+v∈[g̲(x,u,v),g¯(x,u,v)]a.e inRN,u,v∈H1(RN), where f and g are measurable functions that satisfy some technical conditions.
Poly(lactic acid) (PLA) and PLA/5% Babassu compounds were molten mixed, afterwards aged at temperatures ranging from 50 to 90 °C during 15 to 60 min. The aging effect on the phase transitions of PLA compounds was investigated using modulated differential scanning calorimetry (MDSC), through analysis of total, reversing and non-reversing heat flows. The crystallization and melting phenomena were evidenced, as well as the increase of crystalline ordering upon aging. The kinetics of cold crystallization and recrystallization during the melting event were solely elucidated using MDSC. The phase transitions were modeled using Pseudo-Avrami, which displayed good fits between the theoretical and experimental data. This work reports the influence of the composite aging on reordering and recrystallization phenomena of PLA and PLA/Babassu composite with insights of the reordering and recrystallization phenomena.
Preparing blends from fully biodegradable resources is an important alternative in the production of materials less harmful to the environment. Among these materials, thermoplastic cornstarch (TPS) and polycaprolactone (PCL) are an interesting possibility for replacing conventional synthetic materials, and it is desirable that they present relative stability under conditions of processing and use. In the present work, PCL/TPS blends with up to 30% TPS, obtained from cornstarch plasticized with water and glycerin, coconut or babassu oil, were processed in an internal laboratory mixer. Adjusted torque variation rate during the last processing stage is a very sensitive indicator of molar mass alterations with processing time. Rheometry data indicate that TPS obtained with babassu and coconut vegetable oils have a higher molar mass compared to that obtained with glycerin. In addition, the incorporation of TPS promotes thermal degradation in PCL/TPS mixtures, which is more pronounced the higher the TPS content and with TPS-glycerin, except for the PCL/20%TPS blends obtained with glycerin and babassu oil. The mechanical properties of the extruded films decreased with the addition of TPS, this reduction being more evident with the increase in the TPS content and in systems with TPS obtained with babassu oil. In contrast, only in blends containing 10 and 20% TPS of glycerin, there was an increase in elongation at break, being a good feature for flexible films, this property is desirable in certain applications.
A sustentabilidade tem papel fundamental no turismo pois está presente nos fatores ambientais, econômicos e sociais, com destaque ao crescimento do turismo em vinícolas focado na preservação/conservação. A questão central da pesquisa é: qual é a realidade dos estudos científicos sobre enoturismo e sustentabilidade? Como objetivo, o trabalho visa analisar as pesquisas científicas que abordaram a temática do enoturismo e sustentabilidade. A metodologia é composta por um ensaio teórico qualitativo e descritivo feito por meio de pesquisa bibliográfica, com levantamento da produção científica disponível nas bases “WoS” e “Scopus”. A opção pelo termo de busca utilizado foram as palavras-chave "wine tourism" and "sustainability". Os resultados sugerem que as pesquisas sobre a sustentabilidade na cadeia do enoturismo estão crescendo com percepções emergentes e mostram uma concentração geográfica da pesquisa em alguns países como França, Estados Unidos e Brasil. Os consumidores estão se tornando mais sensibilizados sobre as consequências ambientais de suas escolhas, com uma maior atenção às questões sustentáveis na compra de produtos. Conclui-se que ainda existem poucos estudos direcionados para a sustentabilidade no enoturismo e que expliquem como a implantação de práticas de sustentabilidade contribui para o aumento da competitividade de empresas do setor vitivinícola.
This study aimed to evaluate the influence of high hydrostatic pressure (HHP) pretreatment (200 MPa (HHP1) and 400 MPa (HHP 2)) on the drying of plum slices and on the physical, morphostructural and total phenolic compounds of its dust. Drying was carried out at a temperature of 70 °C and an air velocity of 2.0 m s‐1. The application of 400 MPa (HHP2) promoted a 34% reduction in drying time (210 min), higher drying rate and variation in effective diffusivity from 6.703 to 14.273 x 10‐4 m2 min‐1 between the terms of the Check The GAB model was more suitable to determine the equilibrium moisture content (R2>0.99 and P<10%). The plum powders showed a water activity lower than 0.22 (p≥0.05), the increase in HHP promoted an increase in the water solubility index and total phenolic compounds. Larger irregularities such as pores and cavities were observed on the powder surface for HHP2 and the spectra indicated that the intensities of the characteristic bands were significantly altered with the application of HHP. Therefore, the results of this study provide information for the potential application of HHP as a drying pretreatment.
In this paper, the Soft Systems Methodology foundations was integrated to a water resources management model to construct a facilitation process to support integrative water resources management. The facilitation model aims to achieve agreements over conflicts, by promoting engagement of actors to construct a common and holistic understanding about the problematic situation through an interactive, participative, clear, and transparent process. The facilitation model is divided into two phases: (i) Preparing Logistics and (ii) Work meeting. The first phase starts when a conflict emerges, then, the facilitator should prepare the logistics necessary to proceed with the examination of the problem, including the selection of volunteers who will compose the work group. The second phase is intended to the application of an interactive and participatory modeling approach organized into five steps: 1 - Expressing the problematic situation; 2 - Constructing a multi-sectoral representation; 3 - Examining the multi-sectoral representation; 4 - Building a conceptual model; and 5 - Exploring actions. To illustrate its application, we applied these steps to structure a real complex problematic situation that exists in an area of the watershed of the Paraiba do Norte River, in Northeastern Brazil. To construct a multi-sectoral representation of the problem, perspectives of different actors who are involved in the problem were considered. We conclude that the model is a powerful tool for the analysis of complex problems, for which there is no consensus regarding alternatives to solve/mitigate it and/or there is a high level of uncertainties involved in the decision-making process.
Although technology improvements boosted the digital transition of universities, which built a path for smart campuses, the smartization process is more than simply promoting digitalization. This research aims to identify the essential elements and the most significant deficiencies in the smart campus dimensions and its variables from the user’s viewpoint to offer a list of priorities for decision-makers. Through an importance-performance analysis (IPA) performed using IBP SPSS 26, we tested an integrative smart campus framework in a Brazilian university, previously validated with Latin American experts. This research confirmed that eight dimensions are important for a smart campus evaluation and provided a list of priorities for academic managers. The results indicated the main gaps among importance and performance. This research concluded that the smartization process could not rely on technology attributes only. Universities should meet the modern society’s present and emerging needs and the labor market in a sustainable, social, and technological manner. Smart campuses in developing countries may prioritize different components than developed countries, such as infrastructure. We propose that more studies should apply the framework in more universities.
Ultra densification of the number of antennas combined with the use of large bandwidths in the millimeter wave (mmWave) spectrum is considered one of the main methodologies to achieve the quality of service requirements for future generations of wireless communications. Massive multiple-input multiple-output (mMIMO) cell-free (CF) systems have a large number of access points (APs) distributed in the coverage area, serving simultaneously a smaller number of users consuming the same time-frequency resources. In order to support realistic CF networks designs, this work proposes a performance analysis based on ray tracing simulations. The propagation modeling considers reflection, diffraction, diffuse scattering, atmospheric molecular absorption and foliage and rainfall losses. CF networks with APs equipped with multiple antennas operating in the 26 GHz, 38 GHz and 73 GHz bands are evaluated. From the simulation results, the communication channel is characterized and parameterized. Different performance analysis of CF networks are performed, based on downlink spectral efficiency. In addition, the performance of CF networks in rainy environments is evaluated, and it has been observed that this architecture promotes resistance to the effect of rain attenuation.
This study aimed to evaluate the relationship between frailty, sociodemographic and clinical characteristics, and disease severity of older adults with acute coronary syndrome (ACS). A total of 57 hospitalized patients ≥60 years with ACS were assessed for frailty through the Tilburg Frailty Indicator. Disease severity was assessed by the Global Registry of Acute Coronary Events, by the maximum troponin level, and by the number of severely obstructed coronary arteries. The relationship between variables was assessed by Mann Whitney’s test, Pearson’s chi-square test, likelihood-ratio test, Fisher’s exact test, or Student’s t test. Analyses were bootstrapped to 1,000 to reduce potential sample bias. About 54.4% were frail. Frailty was associated with ethnicity ( p = .02), marital status ( p = .05), ischemic equivalents ( p = .01), self-perceived health ( p = .002), arthritis/rheumatism/arthrosis ( p = .002), and number of severely obstructed coronary arteries ( p = .05). These relationships can support intensified surveillance planning for the elderly at greatest risk, structuring of transitional care, appropriate nurse-coordinated secondary prevention delivery in primary care, and cardiac rehabilitation following ACS.
The welding of NiTi shape memory alloys (SMA) can lead to the development of products with complex geometry that would be unfeasible with conventional manufacturing processes such as machining. In this sense, this work aims to study the spot welding of NiTi SMA wires with the tungsten inert gas (TIG) process, which is an alternative to the laser welding often studied for joining SMA. The main objective is to determine TIG spot welding parameters to promote full penetration with a single pulse in NiTi SMA wires with 0.9 mm in diameter. The central rotational compound design method (CRCD) was used as an optimization tool. The weld penetration was evaluated by optical microscopy (OM) and related to input pulse time and power. After evaluation of the interaction effects of time and power factors to obtain results with 95% or more in significance, an equation of the penetration behavior was obtained. The 2D plot of the equation pointed to three optimal parameters, which were evaluated with additional welding tests. All three optimal parameters achieved full penetration, showing that the CRCD method was a great tool to reduce the number of experiments needed in the study of welding parameters. To demonstrate the potential of the TIG spot welding in the fabrication of complex structures of NiTi SMA, a two-dimensional auxetic cell was obtained, showing great structural stability when subjected to tensile tests. Graphical abstract
Leishmanolysin, also known as major promastigote protease (PSP) or gp63, is the most abundant surface glycoprotein of Leishmania spp., and has been extensively studied and recognized as the main parasite virulence factor. Characterized as a metalloprotease, gp63 can be powerfully inactivated in the presence of a metal chelator. In this study, we first used the structural parameters of a 7-hydroxycoumarin derivative, L1 compound, to evaluate the theoretical–computational experiments against gp63, comparing it with an available metal chelator already described. The methodology followed was (i) analysis of the three-dimensional structure of gp63 as well as its active site, and searching the literature and molecular databases for possible inhibitors; (ii) molecular docking simulations and investigation of the interactions in the generated protein–ligand complexes; and (iii) the individual energy of the gp63 amino acids that interacted most with the ligands of interest was quantified by ab initio calculations using Molecular Fraction with Conjugated Caps (MFCC). MFCC still allowed the final quantum balance calculations of the protein interaction to be obtained with each inhibitor candidate binder. L1 obtained the best energy quantum balance result with −2 eV, followed by DETC (−1.4 eV), doxycycline (−1.3 eV), and 4-terpineol (−0.6 eV), and showed evidence of covalent binding in the enzyme active site. In vitro experiments confirmed L1 as highly effective against L. amazonensis parasites. The compound also exhibited a low cytotoxicity profile against mammalian RAW and 3T3 cells lines, presenting a selective index of 149.19 and 380.64 µM, respectively. L1 induced promastigote forms’ death by necrosis and the ultrastructural analysis revealed disruption in membrane integrity. Furthermore, leakage of the contents and destruction of the parasite were confirmed by Spectroscopy Dispersion analysis. These results together suggested L1 has a potential effect against L. amazonensis, the etiologic agent of diffuse leishmaniasis, and the only one that currently does not have a satisfactory treatment.
Giardiasis is a neglected disease, and there is a need for new molecules with less side effects and better activity against resistant strains. This work describes the evaluation of the giardicidal activity of thymol derivatives produced from the Morita–Baylis–Hillman reaction. Thymol acrylate was reacted with different aromatic aldehydes, using 1,4-diazabicyclo[2.2.2]octane (DABCO) as a catalyst. Eleven adducts (8 of them unpublished) with yields between 58 and 80% were obtained from this reaction, which were adequately characterized. The in silico prediction showed theoretical bioavailability after oral administration as well as antiparasitic activity against Giardia lamblia. Compound 4 showed better biological activity against G. lamblia. In addition to presenting antigiardial activity 24 times better than thymol, this MBHA was obtained in a short reaction time (3 h) with a yield (80%) superior to the other investigated molecules. The molecule was more active than the precursors (thymol and MBHA 12) and did not show cytotoxicity against HEK-293 or HT-29 cells. In conclusion, this study presents a new class of drugs with better antigiardial activity in relation to thymol, acting as a basis for the synthesis of new bioactive molecules. Graphic abstract Molecular hybridization technique combined with the Morita–Baylis–Hillman reaction provided new thymol derivatives with giardicidal activity superior to the precursor molecules.
The Caatinga region, one of the world's most biodiverse tropical drylands, has been recently portrayed as an aggregate of closed biotas that do not interact despite being contiguous. Here, we demonstrate that, in contrast with this view, the Caatinga region is a dynamic and heterogeneous system whose major characteristics are shaped by multiple ecological and evolutionary processes operating across different spatial and temporal scales. This systemic perspective fits better with modern ecology and biogeography and provides a more robust framework for regional conservation plans. We conclude by outlining a research agenda that seeks to fill some of the most important knowledge gaps on the Caatinga's biodiversity.
Extensive experimental and theoretical studies have been performed in recent decades regarding the effect of the rates of change of temperature on the glass transition temperature, Tg, and the width of the glass transition interval, δTg. In this paper, we push forward the frontiers of knowledge obtained in this direction by performing a detailed analysis of the dependence of Tg and δTg obtained in subsequent heating on the initial glass densities, which were reached after prolonged preliminary sub-Tg annealing. Our experiments show that Tg increases and δTg decreases with increasing the initial glass density. By treating the structural relaxation time as a function of temperature and density, we develop a theoretical model that successfully describes both the density changes in annealing and the resulting variations of the glass transition temperature and the width of the glass transition interval in subsequent heating. These findings are relevant to understand glass annealing and its effect on devitrification in subsequent heating - two phenomena of major importance in glass science and technology.
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2,892 members
Francisco de Assis
  • Departamento de Engenharia Elétrica - DEE
Roberio Gomes Olinda
  • Centro de Saúde e Tecnologia Rural – CSTR (Campus de Patos)
Luciano Nascimento
  • Department of Physical and Inorganic Chemistry and Reactions
Francisco Brasileiro
  • Departamento de Sistemas e Computação (DSC)
Magnólia Campos
  • Unidade Acadêmica de Biologia e Química - UABQ
Campina Grande, Brazil