Federal University of Amazonas
  • Manaus, Amazonas, Brazil
Recent publications
There are many claims that gamification (i.e., using game elements outside games) impact decreases over time (i.e., the novelty effect). Most studies analyzing this effect focused on extrinsic game elements, while fictional and collaborative competition have been recently recommended. Additionally, to the best of our knowledge, no long-term research has been carried out with STEM learners from introductory programming courses (CS1), a context that demands encouraging practice and mitigating motivation throughout the semester. Therefore, the main goal of this work is to better understand how the impact of a gamification design, featuring fictional and competitive-collaborative elements, changes over a 14-week period of time, when applied to CS1 courses taken by STEM students (N = 756). In an ecological setting, we followed a 2x7 quasi-experimental design, where Brazilian STEM students completed assignments in either a gamified or non-gamified version of the same system, which provided the measures (number of attempts, usage time, and system access) to assess user behavior at seven points in time. Results indicate changes in gamification’s impact that appear to follow a U-shaped pattern. Supporting the novelty effect, the gamification’s effect started to decrease after four weeks, decrease that lasted between two to six weeks. Interestingly, the gamification’s impact shifted to an uptrend between six and 10 weeks after the start of the intervention, partially recovering its contribution naturally. Thus, we found empirical evidence supporting that gamification likely suffers from the novelty effect, but also benefits from the familiarization effect, which contributes to an overall positive impact on students. These findings may provide some guidelines to inform practitioners about how long the initial contributions of gamification last, and how long they take to recover after some reduction in benefits. It can also help researchers to realize when to apply/evaluate interventions that use gamification by taking into consideration the novelty effect and, thereby, better understand the real impact of gamification on students’ behavior in the long run.
A new method, the complex impedance formalism, is presented to disclose the relaxation process of conducting materials. This method is an extrapolation of the dielectric modulus formalism in the Bode representation of the impedance. As in the dielectric modulus formalism, the relaxation process can be approached in both the frequency and time domains for non-Debye relaxation type. The complex impedance formalism is tested by analysis of the relaxation process of the solid BaTiO3 material at high temperatures. A combination of complex impedance and dielectric modulus formalism provides us with a better understanding concerning individual relaxation regions. The complex impedance formalism allows the hidden relaxation process at low frequency regime to be accessible, whereas the dielectric modulus formalism discloses the relaxation process at high frequency in mixed electronic-ionic conductors.
In the Amazon Basin, large-scale problems, such as deforestation, over-fishing, climate change and large hydroelectric dams, are now recognized. However, many small-scale activities could exert significant cumulative, negative environmental impacts. We conducted a spatial analysis of small-scale dams used for hydropower and aquaculture in the central and southwestern portions of the Brazilian Amazon Basin. We found a very high density of small dams in these areas, and suggest that these dams, in the aggregate, are in fact pernicious because they are likely to have large impacts on the aquatic environment of these sub-basins in the Amazon. We recommend increasing the size and number of protected areas where dams are not allowed, and restricting the number of licenses for dams in order to reduce future intensification of their impacts.
The low availability of phosphorus (P) in tropical soils may hinder the initial establishment of forest species planted in disturbed areas. However, the effects of P fertilization as a strategy to improve the survival, growth and photosynthesis-related traits of Amazonian tree species in P-limited soils remain unclear. Here, we investigate how contrasting levels of P fertilization affect the establishment of native Amazonian tree species with different successional statuses. We measured the survival, growth (height and root collar diameter) and leaf traits (e.g., chlorophyll a fluorescence parameters, leaf nutrients and gas exchange) of ten species (five pioneers and five nonpioneers) subjected to contrasting P supplies (−P = 0 kg P2O5 ha−1 and +P = 160 kg P2O5 ha−1) in the field over 24 months. Phosphorus fertilization improved the availability of P in the soil. Pioneers species were more responsive to fertilization. Erythrina fusca showed high mortality under −P, while Cedrela fissilis, Cordia alliodora and Guazuma ulmifolia (pioneers) exhibited the highest increases in growth rates after fertilization. Fertilization improved the P content in the leaves in the noonpioneers group, while both ecological groups had the highest K content in the leaves under no P fertilization. Carbon capture (stomatal conductance) increased only in pioneers species. Conversely, positive effects on carbon assimilation at the leaf level were not observed. P fertilization reduced the P use efficiency of nonpioneers species. Fertilization is an important management practice to relieve the effects of stress induced by soil phosphorus starvation on the establishment of Amazonian trees and is modulated by successional status and species identity.
This paper presents a new approach for detecting malaria parasites in full images of thick blood smear using pixel classifiers for obtaining foreground objects and delimiting parasite-stained objects. For both processes, the HSV components were used as input variables of the following pixel classifiers: multilayer perceptron and a decision tree. The obtained patches were classified using a deep neural network with 34 layers, trained from scratch. The image dataset used was divided into sets with different parasite sizes. This enables characterizing performance metrics (accuracy, sensitivity, specificity, precision, and F1-score) for parasite detection with varying parasite sizes. The best metric values were obtained in images with large parasite sizes. For image sets 1 and 2, with large parasite sizes, precision rates of 91.71% and 93.14% were obtained. For image sets 3 and 4, with small parasite sizes, precision rates of 76.58% and 71.58% were obtained. As shown by the literature review, these results are comparable to others previously published. Nevertheless, a rigorous comparison could not be done, as different works use different datasets.
Bacterial Cellulose (BC) production is still considered expensive and challenging for industries. Herein, BC was produced through an acetic acid bacteria isolated from the kombucha consortium and an extract from acerola juice-industrial waste. The isolated bacterium was characterized through different assays (biochemical characterization and 16S rRNA gene) being identifed as Komagataeibacter rhaeticus. BC production with static cultivation mode by the isolated strain was compared using traditional Hestrin-Schramm (HS) medium and acerola waste (AC) (5% w/v). The kinetic behavior of BC production was slightly higher in the HS medium reaching 2.9 g/L after 12 days of fermentation, while 2.3 g/L in the AC medium. Minor differences were observed between crystallinity, crystallite size, and d-spacing, highlighting BC produced by the AC medium twofold breaking stress resistance compared to the conventional medium, with high-temperature stability and economically feasible, promissory results for further application of this synthesized cellulose obtained from industrial residues.
User eXperience (UX) evaluations play an essential role in the software development process. As the results from such evaluations can drive future releases, it is necessary to identify which factors can substantially change users’ judgments about their experience to have more precise results and understand UX better. This article investigates how interaction sequencing, previous experience, and the number of problems could affect overall satisfaction and the two main UX dimensions: pragmatic and hedonic. We employed three different evaluation methods to evaluate a chatbot-based mobile shopping application. The results revealed that participants with previous experience with similar apps tended to give lower ratings. We also found that as inspectors identify more problems, they tend to rate the pragmatic dimension lower. Finally, we did not identify a significant influence of interaction sequencing on UX evaluation. We discuss the reasons for these results, the implications for practitioners and researchers, and research opportunities.
The study of the morphology and hydrodynamics of large rivers has advanced in recent decades. Nonetheless, there are a few studies with surveyed data carried out at the confluences of the mega rivers (Q > 17,000 m³s−1), especially those from the Amazon basin. The Negro River is the main river in the northwestern Amazon and is considered the sixth-largest in the world in terms of water discharge, has a complex multichannel pattern and a peculiar geological configuration. This article aims at analyzing the bed morphology and hydrological processes in the confluence region between the Branco and Negro rivers. Field surveys with echo-sounding and Acoustic Doppler Current Profiler were carried out over an area of 31 km2 during the low water period of 2021 year. The results of this survey made it possible to identify the main morphological characteristics of the riverbed in the confluence hydrodynamic zone between Branco and Negro River, as well as the dynamics of the velocity, streamflow, and transport of suspended sediment of these important northwestern Amazonian rivers. Analysis of bed morphology and their neotectonic control are also discussed. These results presented in this work contribute to expanding the knowledge about the confluence of large tropical rivers with significant bed discordance and differences in the density of flows.
Background To examine the role of dental pain, sense of coherence (SOC) and social support on the relationship between dental caries and oral health-related quality of life (OHRQoL) in children aged 12 years. Methods A cross-sectional study involving 400 schoolchildren selected from public schools in a socioeconomically disadvantaged region in the city of Manaus, Brazil was carried out. The predictors of OHRQoL were selected according to the Wilson and Cleary theoretical model, including number of decayed teeth and its clinical consequence (component D of the DMFT index and PUFA/pufa index), dental pain (symptom status), and SOC and social support (individual and environmental characteristics). Statistical analysis was conducted through structural equation modelling and multivariable negative binomial regression. The significance level established for all analyses was 5%. Results Number of dental caries was indirectly linked with OHRQoL (β = 0.19, 95% CI 0.11/0.29) through dental pain, SOC and social support. Clinical consequences of untreated caries directly predicted poor OHRQoL (β = 0.12, 95% CI 0.01/0.23). Dental pain, SOC and social support did not moderate the effect of dental caries measures on OHRQoL. Conclusion Our findings suggest the role of dental pain, SOC and social support as mediator factors on the link between dental caries and OHRQoL. Tackling dental caries along with psychosocial factors may attenuated the impact of oral health on OHRQoL in children.
Andean purple maize (APM) is an ancient crop widely used as a natural coloring in traditional Peruvian cuisine. However, it has been little explored within the food industry. The present study assessed how APM impacts on techno‐functional properties and sensory acceptance of breakfast cereals. Extruded samples formulated with 100, 75, 50, and 25% APM, and complemented with yellow corn grits (YCG), were analyzed for their techno‐functional and sensory properties. Increases in bulk density, as well as reduction in the expantion and porosity were observated for extrudates containing ≥ 50% APM, accompanied by an increase in purple color intensity. Increase in milk absorption index, reduction in milk solubility index and decreased in cereal hardness with increase in APM were also observed. Despite this, APM extented the cereal bowl‐life. High sensory scores of overall liking (6) and color (7) were obtained for extruded formulations containing ≥ 50% APM and low values for extrudates with 25% APM. Aroma, flavor, and texture scores did not present significant differences. APM is an ingredient with the potential to be used to produce breakfast cereals since it improves their techno‐functional characteristics and sensory acceptance, at the same time, it leads to the production of healthy, nutritious, and sustainable food. This article is protected by copyright. All rights reserved.
A new systematic structural study was performed using the Atomic Force Microscopy (AFM) reporting statistical parameters of polymeric particles based on gelatin and poly-ε-caprolactone (PCL) containing essential oil from Lippia origanoides. The developed biocides are efficient alternative controlling agents of Conotrachelus humeropictus and Moniliophtora perniciosa, the main pests of Theobroma grandiflorum. Our results showed that the particles morphology can be successfully controlled by advanced stereometric parameters, pointing to an appropriate concentration of encapsulated essential oil according to the particle surface characteristics. For this reason, the absolute concentration of 1000 µg·mL−1 (P1000 system) was encapsulated, resulting in the most suitable surface microtexture, allowing a faster and more efficient essential oil release. Loaded particles presented zeta potential around (–54.3 ± 2.3) mV at pH = 8, and particle size distribution ranging from 113 to 442 nm. The hydrodynamic diameter of 90% of the particle population was found to be up to (405 ± 31) nm in the P1000 system. The essential oil release was evaluated up to 80 h, with maximum release concentrations of 63% and 95% for P500 and P1000, respectively. The best fit for the release profiles was obtained using the Korsmeyer–Peppas mathematical model. Loaded particles resulted in 100% mortality of C. humeropictus up to 48 h. The antifungal tests against M. perniciosa resulted in a minimum inhibitory concentration of 250 µg·mL−1, and the P1000 system produced growth inhibition up to 7 days. The developed system has potential as alternative controlling agent, due to its physical stability, particle surface microtexture, as well as pronounced bioactivity of the encapsulated essential oil.
Considerable efforts have been spent on environmentally friendly particles for the encapsulation of essential oils. Polymeric particles were developed to encapsulate the essential oil from Piper nigrum based on gelatin and poly-ε-caprolactone (PCL) carriers. Gas Chromatography ((Flame Ionization Detection (GC/FID) and Mass Spectrometry (GC/MS)), Atomic Force Microscopy (AFM), Nanoparticle Tracking Analysis (NTA), Confocal Laser Scanning Microscopy (CLSM), Attenuated Total Reflectance-Fourier-transform Infrared Spectroscopy (ATR-FTIR), and Ultraviolet-Visible (UV-VIS) spectroscopy were used for the full colloidal system characterization. The essential oil was mainly composed of β-caryophyllene (~35%). The stability of the encapsulated systems was evaluated by Encapsulation Efficiency (EE%), electrical conductivity, turbidity, pH, and organoleptic properties (color and odor) after adding different preservatives. The mixture of phenoxyethanol/isotialzoni-3-one (PNE system) resulted in enhanced stability of approximately 120 and 210 days under constant handling and shelf-life tests, respectively. The developed polymeric system presented a similar controlled release in acidic, neutral, or basic pH, and the release curves suggested a pulsatile release mechanism due to a complexation of essential oil in the PCL matrix. Our results showed that the developed system has potential as an alternative stable product and as a controlling agent, due to the pronounced bioactivity of the encapsulated essential oil. Citation: Azevedo, S.G.; Rocha, A.L.F.; de Aguiar Nunes, R.; da Costa Pinto, C.; Ţălu, Ş.; da Fonseca Filho, H.; de Araújo Bezerra, J.; Lima, A.R.; Guimarães, F.E.G.; Campelo, P.H.; et al. Pulsatile Controlled Release and Stability Evaluation of Polymeric Particles Containing Piper nigrum Essential Oil and Preservatives. Materials 2022, 15, 5415.
The great interest in flix-like services has amplified multimedia traffic over the Internet. Recently released traffic forecasting predicts that video-related traffic will be responsible for the majority of Internet traffic by 2022. Such traffic will come in a wide range of duration and in the two modes of live and on-demand. Additionally, it is expected to scale and deliver a smoothed experience to an already fragmented audience. The adaptive bitrate over Hypertext Transfer Protocol (HTTP) has emerged as the top technology for multimedia content transport and delivery. Despite the large amount of work in this area, running streaming applications on overload channels still demands the development of effective strategies. In this work, a video bitrate adaptation mechanism deployed in an overloaded channel of an access network is proposed and evaluated under live and on-demand service modes. This mechanism makes decisions regarding bitrate switching based on the Quality of Experience (QoE)-related parameters to accommodate conflicting variables of its design space, namely, image quality, session continuity and short play time. To evaluate this mechanism, a multifactor QoE metric is proposed based on session parameters such as stalls, startup delay, image quality and the mechanism bitrate misalignment. Moreover, in the numerical studies for the evaluation of the effectiveness of the proposed mechanism, the average video bitrate, instability and fairness are measured. Overall, the proposed mechanism was able to improve the session QoE for both live and on-demand modes.
In this study, a thiazolopyrimidine derivative ethyl 2-(2-acetoxyphenyl)-5-(4 (benzyloxy) phenyl)-7-methyl-3-oxo-3,5-dihydro-2H-thiazolo[3,2-a]pyrimidine-6 carboxylate (EAPC) was investigated experimentally and theoretically. FMOs (frontier molecular orbitals), MEP, ALIE surfaces and solvation free energies were calculated for EAPC at CAM-B3LYP/6–311++G(2d,p) level. Solvation free energies in water, ethanol, acetone, acetonitrile, and chloroform were obtained and the analysis of the energy values suggests that acetone and acetronitrile may be better for solubilization of EAPC. However, the value of solvation energy in water (hydration free energy) indicates good solubility of the studied molecule in an aqueous medium, factor that corroborates the biological activity. Vibrational analysis, together with potential energy distribution (PED) calculations, revealed several characteristic vibrations. Molecular docking and molecular dynamics simulations carreid out with angiotensin I-converting enzyme revealed that EAPC is a promising antihypertensive candidate.
This study investigated flexible, freestanding niobium pentoxide (Nb2O5) decorated multiwalled carbon nanotube (MWCNT) electrode material in a sodium-ion pseudocapacitor and its respective energy storage mechanism. Sodium is an abundant element in the Earth's crust, with attractive sustainability and low-cost appeal for the scientific community and energy markets such as electric vehicles and renewable energies. Combined with niobium pentoxide and carbon nanotubes, sodium ions can perform ultra-fast intercalation into niobium pentoxide and electrostatic adsorption onto carbon high surface areas. Niobium pentoxide particles were investigated using X-ray diffraction via Rietveld refinement, a powerful technique to study crystalline materials' electronic and structural properties that directly influence Na⁺-ion diffusion. The niobium pentoxide-decorated MWCNT electrode material was investigated within a symmetric supercapacitor (SIC) and as an anode for sodium-ion batteries (SIBs). A finite-length transmission line was used to model the impedance behavior of the solid and liquid phases that comprised the material/solution interface. This numerical modelling allowed investigators to infer the presence of MWCNT as a nanostructured matrix since Nb2O5 dispersive nanoparticles increased the overall pseudopacacitance by 63.2% for Nb2O5/MWCNT compared to MWCNT nanostructured electrodes. Electrochemical findings revealed a maximum capacitance of 192 F g⁻¹ for the SIC full cell, with capacitance retention of 96% after 10,000 cycles. In addition, the SIC delivered outstanding power density from 98.7 to 24,671 W kg⁻¹ and high energy density from 5.4 to 2.7 W h kg⁻¹. In an SIB half-cell configuration, the electrode delivered a reversible sodium-ion storage capacity of ~163 mA h g⁻¹, with a retention capacity of ~68 mA h g⁻¹ after 100 cycles at 25 mA g⁻¹. These systems bridge the gap between supercapacitors and batteries by employing the best properties of them both.
and socioeconomic development. Total concentrations of the markers analyzed ranged from 21.0 to 103.8 ng g −1 , 450.2 to 2390.2 ng g −1 , and 233.8 to 9827.3 ng g −1 for ∑ PAHs , ∑ n-alk , and ∑ sterols , respectively. Concentrations and patterns of PAH, AH, and sterol ratio distribution changed over time and may be associated with different episodes in the history of the city of Fortaleza. The marker ratio distribution in the sediment core revealed an overlap of natural and Abstract In this study, the multi-marker approach was used for the first time with a highly urbanized lake located in the city of Fortaleza, Brazil, to provide a comprehensive view of temporal trends in sources of pollutants and evaluate the relation between the influence of anthropogenic activities Supplementary Information The online version contains supplementary material available at https:// doi.
Trichlorfon is a widely used drug to control ectoparasites in fish farming and is effective in treating protozoa, helminths, and crustaceans. However, prior to a concentration recommendation made for therapeutic purposes in aquaculture, it is necessary to establish its toxicity, behavioural and histological effects, and determine a safe use dose for each target species. Here we investigated the acute toxicity (LC50-12 h) of trichlorfon and its behavioural and histological effects on arapaima (Arapaima gigas) larvae and juveniles. For the acute toxicity tests (LC50), arapaima larvae and juveniles were exposed at 0, 50, 250, 500, 750, 1.000 and 1.250 mg L⁻¹ of trichlorfon for 12 h. During this period, behavioural changes, mortality, and the water physico-chemical parameters were recorded. Immediately after a toxicity test, gills were collected for the histological analysis. The LC50–12 h for the arapaima larvae and juveniles were 411.8 mg L⁻¹ and 587.3 mg L⁻¹, respectively. The fish exposed for different times to the 250, 500, 750, 1.000 and 1.250 mg L⁻¹ concentrations showed a dose-dependent effect with behavioural changes, such as erratic swimming, loss of balance, lethargy, gasping at the water surface and muscle spasms. Histological changes, such as lamellar hyperplasia and cell hypertrophy, total lamellar fusion, dilation, and vascular congestion in the central filament vessel, interlamellar hyperplasia, capillary congestion, proliferation of mucous cells, dilation of the venous sinus and capillaries, leukocyte infiltrate and haemorrhage, were observed and ranged from mild to diffuse lesions. However, branchial necrosis was presented only in the fish exposed to ≥ 500 mg L⁻¹ of trichlorfon. In conclusion, sublethal trichlorfon concentrations (≤ 250 mg L⁻¹) and short exposure times (up to 180 min) can be safely used in arapaima larvae and juveniles because they do not alter their normal behaviour nor induce mortalities and/or irreversible injuries to their gills.
In this work, we investigated in vitro different biological activities of alkaline lignins extracted from the species Buchenavia viridiflora, a tree from the Amazon rainforest used as a wood product. The chemical composition results for the twig and leaves were, respectively (%): cellulose (30.88 and 24. 28), hemicellulose (21.62 and 23.03), lignin (29.93 and 25.46), extractives (13.06 and 20.52), and ash (4.51 and 6.72). The yield was higher for the lignin of the branches (67.9 %) when compared to the leaves (60.2 %). Lignins are of the GSH type, low molecular weight and thermally stable. They promoted moderate to low antioxidant activity, highlighting the lignin of the branches, which presented an IC50 of 884.56 μg/mL for the DPPH assay and an IC50 of 14.08 μg/mL for ABTS. In the cytotoxicity assays, they showed low toxicity against macrophage cells (IC50 28.47 and 22.58 μg/mL). In addition, they were not cytotoxic against splenocytes and erythrocytes at concentrations ranging from 100 to 6.25 μg/mL. These were able to promote splenocyte proliferation and induce the production of anti-inflammatory cytokines. And inhibit the growth of tumor cells with IC50 ranging from 12.63 to values >100 μg/mL and microbial at a concentration of 512 μg/mL. Finally, they showed antiparasitic activity by inhibiting the growth of chloroquine-sensitive and resistant Plasmodium falciparum strains. These findings reinforce that the lignins in this study are promising for potential pharmaceutical and biomedical applications.
Researchers and practitioners are becoming aware of the importance of User eXperience (UX) in mobile app development. Developing merely usable apps became insufficient to meet users’ needs, requiring developers to focus on promoting pleasurable experiences to get a competitive advantage. To that end, it is crucial to understand what factors can lead to positive or negative UX. In this scenario, app store reviews emerged as a valuable source to address UX issues from analyzing several self-reports of end-users experiences in the wild. Many researchers have proposed approaches to analyze such reviews and investigate the effect of factors related to the user (e.g., gender, culture) and the app (e.g., bugs, features) on UX. However, the fragmentation of the results into various studies makes it difficult to draw conclusions that can support the development process and advance the research in the field. This paper presents a systematic mapping study to address publications that analyze app store reviews and identify the factors affecting UX reflected on users’ ratings and sentiment. From 25 accepted publications, we extracted 31 factors and their associated polarities. We also identified research gaps and future work opportunities with implications for practitioners and researchers.
Recent outbreaks of infectious diseases such as Covid-19 that have fever as one of the symptoms drive the search for systems to track people with fever quickly and non-contact, also known as sanitary barriers. The use of non-contact infrared-based instruments, especially the infrared thermal imager, has widely spread. However, the screening process has presented low performance. This article addresses the choice of regions of interest on the human face for the analysis of the individual's fever, deals with the temperature thresholds used for this analysis, as well as the way to issue the recommendation to screen the person or not. The data collection and statistical analysis of temperatures of 198 volunteers allowed us to study and define the most appropriate face regions as targets for these barriers, as well as the temperature thresholds to be used for screening for each of these regions. Besides, the paper presents a probabilistic method based on the metrological quality of the sanitary barrier to the emission of recommendation for screening potentially febrile people. The developed method was tested in feverish and non-febrile volunteers, showing complete assertiveness in the tested cases.
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2,230 members
Karla De jesus
  • Physical Education and Physioteraphy
Vicente Lucena Jr
Naziano Filizola Jr
  • Department of Geosciences
Maria Francisca Simas Teixeira
  • Departamento de Parasitologia
Adolfo Mota
  • Department of Fundamental Sciences and Agricultural Development
Av. General Rodrigo Octávio, 6200, Coroado I, CNPJ: 04.378.626/0001-97 , 69077-000, Manaus, Amazonas, Brazil
Head of institution
Sylvio Mario Puga Ferreira
+55 (92) 3305-4513