Estimation of soil phosphorus availability via visible and near-infrared spectroscopy

Spectroscopic techniques have great potential to evaluate soil properties. However, there are still questions regarding the applicability of spectroscopy to analyze soil phosphorous (P) availability, especially in tropical soils with low nutrient contents. Therefore, this study evaluated the possibility to estimate P availability in soil and its pools (labile, moderately labile and non-labile) via Vis-NIR spectroscopy based on intra-field calibration. We used soils from two different locations, a plot experiment that received application of phosphate fertilizers (Field-A) and a cultivated field where a grid soil sampling was performed (Field-B). We used the technique of diffuse reflectance in the visible and near-infrared (Vis-NIR) to obtain the spectra of soil samples. Predictive modeling for P availability and labile, moderately labile and non-labile pools of P in soil were obtained via partial least squares (PLS) regression; classification modeling was performed via Soft Independent Modeling of Class Analogy (SIMCA) on three P availability levels in order to overcome the limitation on quantifying P via Vis-NIR spectroscopy. We found that isolating P contents as the only variable (Field-A), Vis-NIR spectroscopy does not allow estimating P pools in the soil. In addition, quantification of P available in the soil via predictive modeling has limitations in tropical soils. On the other hand, estimating P content in soil through classes of availability is a feasible and promising alternative

Resistência à compressão e viabilidade econômica de blocos de concreto dosado com resíduos de tijolos cerâmicos

Os tijolos e blocos cerâmicos são empregados em larga escala nas construções das alvenarias de vedação ouestruturais, proporcionando condições adequadas de conforto ao ambiente interno. Na fabricação desses elementoscerâmicos há necessidade de se excluir as peças com defeitos, originados da não conformidade dasdimensões, das falhas no processo de queima ou quebras. O simples descarte dessas peças com defeito ematerros gera custos de remoção e impactos ambientais, bem como o desperdício de um material que contémsuas propriedades físicas e mecânicas inerentes. Nesse contexto, o presente trabalho teve como objetivo avaliar,sob os aspectos da resistência à compressão e econômicos, a viabilidade do emprego de agregados oriundosdo resíduo de tijolos cerâmicos na dosagem de concreto para produção de blocos maciços para pavimentaçãoe para alvenaria. Para tanto, foram triturados tijolos cerâmicos, em moinho de martelos e elaboradasmisturas de concreto com substituição dos agregados (miúdo e graúdo). O desempenho mecânico dosblocos produzidos foi avaliado por ensaio à compressão simples e a viabilidade econômica para implantaçãodo processo de aproveitamento dos resíduos foi analisada para cenários com um horizonte de cinco anos,utilizando o fluxo de caixa para calcular o retorno do investimento inicial. Os resultados mostraram que osblocos produzidos com a substituição de 80% do agregado miúdo apresentaram um elevado desempenhomecânico e comprovada viabilidade econômica. Com base nestes resultados, conclui-se que a produção deblocos para pavimentação e alvenaria é uma solução viável para o aproveitamento e destino dos resíduos daindústria cerâmica.Palavras-chave: agregados cerâmicos; descarte de olaria; aproveitamento de resíduos; fluxo de caixa; planode produção

Effects of High-Intensity Warm-Up on 5000-Meter Performance Time in Trained Long-Distance Runners

Warm-up protocols with high intensities before continuous running provide potential benefits for middle-distance runners. Nevertheless, the effect of high-intensity warm-ups on long-distance runners remains unclear. The purpose of this study was to verify the effect of a high-intensity warm-up protocol on 5000 m performance in trained runners. Thirteen male runners (34 ± 10 years, 62 ± 6 kg, 62.7 ± 5.5 ml/kg/min) performed two 5000 m time trials, preceded by two different warm-ups. One high-intensity warm up (HIWU: 1x 500 m (70% of the running intensity) + 3x 250 m (100% of the running intensity) and one low-intensity warm up (LIWU: 1x 500 m (70% of the running intensity) + 3x 250 m (70% of the running intensity)), where the running intensities were calculated using the results obtained in the Cooper test. Physiological and metabolic responses, and endurance running performance parameters, were evaluated by the Counter Movement Jump (CMJ), running rating of perceived exertion (RPE), blood lactate concentration (BLa), and performance running. Total time for the 5000 m was lower using HIWU when compared to LIWU (1141.4 ± 110.4 s vs. 1147.8 ± 111.0 s; p = 0.03; Hedges' g = 0.66). The HIWU warm-up led to an improvement in pacing strategy during the time trial. After warm-up protocols, the performance on the CMJ was improved only when applying HIWU (p = 0.008). Post warm-up BLa was significantly higher for HIWU vs. LIWU (3.5 ± 1.0 mmol·L-1 vs. 2.3 ± 1.0 mmol·L-1; p = 0.02), with similar behavior for the RPE (p = 0.002), internal load of the session (p = 0.03). The study showed that a high-intensity warm-up protocol can improve performance in the 5000 m in trained endurance runners

Acute Neuromuscular, Physiological and Performance Responses After Strength Training in Runners: A Systematic Review and Meta-Analysis

Background: Strength training (ST) is commonly used to improve muscle strength, power, and neuromuscular adaptations and is recommended combined with runner training. It is possible that the acute effects of the strength training session lead to deleterious effects in the subsequent running. The aim of this systematic review and meta-analysis was to verify the acute effects of ST session on the neuromuscular, physiological and performance variables of runners. Methods: Studies evaluating running performance after resistance exercise in runners in the PubMed and Scopus databases were selected. From 6532 initial references, 19 were selected for qualitative analysis and 13 for meta-analysis. The variables of peak torque (PT), creatine kinase (CK), delayed-onset muscle soreness (DOMS), rating of perceived exertion (RPE), countermovement jump (CMJ), ventilation (VE), oxygen consumption (VO2), lactate (La) and heart rate (HR) were evaluated. Results: The methodological quality of the included studies was considered reasonable; the meta-analysis indicated that the variables PT (p = 0.003), DOMS (p < 0.0001), CK (p < 0.0001), RPE (p < 0.0001) had a deleterious effect for the experimental group; for CMJ, VE, VO2, La, FC there was no difference. By qualitative synthesis, running performance showed a reduction in speed for the experimental group in two studies and in all that assessed time to exhaustion. Conclusion: The evidence indicated that acute strength training was associated with a decrease in PT, increases in DOMS, CK, RPE and had a low impact on the acute responses of CMJ, VE, VO2, La, HR and submaximal running sessions. Keywords: Aerobic performance; Competitive training; Running; Strength training

Acute effects of transcranial direct current stimulation (tDCS) on peak torque and 5000 m running performance: a randomized controlled trial

The benefits of transcranial direct current stimulation (tDCS) on brain function, cognitive response, and motor ability are well described in scientific literature. Nevertheless, the effects of tDCS on athletes’ performance remain unclear. To compare the acute effects of tDCS on the running performance of 5000 m (m) runners. Eighteen athletes were randomized into Anodal (n = 9) groups that received tDCS for 20 min and 2 mA, and Sham (n = 9), in the motor cortex region (M1). Running time in 5000 m, speed, perceived exertion (RPE), internal load and peak torque (Pt) were evaluated. The Shapiro–Wilk test followed by a paired Student’s t-test was used to compare Pt and total time to complete the run between the groups. The running time and speed of the Anodal group (p = 0.02; 95% CI 0.11–2.32; d = 1.24) was lower than the Sham group (p = 0.02, 95% CI 0.05–2.20; d = 1.15). However, no difference was found in Pt (p = 0.70; 95% CI − 0.75 to 1.11; d = 0.18), RPE (p = 0.23; 95% CI − 1.55 to 0.39; d = 0.60) and internal charge (p = 0.73; 95% CI − 0.77 to 1.09; d = 0.17). Our data indicate that tDCS can acutely optimize the time and speed of 5000 m runners. However, no alterations were found for Pt and RPE

Ultramarathon Evaluation above 180 km in relation to Peak Age and Performance

Background. Ultramarathons with distances over 180 km might lead to different results regarding participation, performance, and age compared to shorter runs of 50 and 100 km. Objective. To evaluate ultramarathons with distances above 180 km in relation to runners’ peak age and performance. Methods. Verification of the quantity of competitions in runs over 180 km by continents in the period 2000 to 2020 and evaluation of the individual results of 13,300 athletes after 2010. Results. Europe stood out with the largest number of organized events, followed by Asia and North America. The age peak performance (PP) in men and women averaged 45 years old with relationship between (, ; ). Men accounted for more than 80% of the runners and showed a reduction in PP from 2015 onwards (). Competitions between 180 and 240 km were the most frequent, particularly after 2016, surpassing the number of marathons over 360 km (). Men and women showed higher velocity in distances () from 180 to 240 km when compared to 241 to 300 k m, 301 to 360 km, and >360 km courses. Conclusions. The decade between 2010 and 2020 showed an increase in the number of Ultramarathon running events. Europe had the highest number. Women had low participation. Performance progression fell, a fact associated with an increase in the number of participants and not specifically related to a decline in athletic performance over the years

Effects of High-Intensity Warm-Up on 5000-Meter Performance Time in Trained Long-Distance Runners

Warm-up protocols with high intensities before continuous running provide potential benefits for middle-distance runners. Nevertheless, the effect of high-intensity warm-ups on long-distance runners remains unclear. The purpose of this study was to verify the effect of a high-intensity warm-up protocol on 5000 m performance in trained runners. Thirteen male runners (34 ± 10 years, 62 ± 6 kg, 62.7 ± 5.5 ml/kg/min) performed two 5000 m time trials, preceded by two different warm-ups. One high-intensity warm up (HIWU: 1x 500 m (70% of the running intensity) + 3x 250 m (100% of the running intensity) and one low-intensity warm up (LIWU: 1x 500 m (70% of the running intensity) + 3x 250 m (70% of the running intensity)), where the running intensities were calculated using the results obtained in the Cooper test. Physiological and metabolic responses, and endurance running performance parameters, were evaluated by the Counter Movement Jump (CMJ), running rating of perceived exertion (RPE), blood lactate concentration (BLa), and performance running. Total time for the 5000 m was lower using HIWU when compared to LIWU (1141.4 ± 110.4 s vs. 1147.8 ± 111.0 s; p = 0.03; Hedges' g = 0.66). The HIWU warm-up led to an improvement in pacing strategy during the time trial. After warm-up protocols, the performance on the CMJ was improved only when applying HIWU (p = 0.008). Post warm-up BLa was significantly higher for HIWU vs. LIWU (3.5 ± 1.0 mmol·L-1 vs. 2.3 ± 1.0 mmol·L-1; p = 0.02), with similar behavior for the RPE (p = 0.002), internal load of the session (p = 0.03). The study showed that a high-intensity warm-up protocol can improve performance in the 5000 m in trained endurance runners

SOIL LOSSES IN THE CEDRO RIVER BASIN/MG BASED ON THE SENSOR TM/LANDSAT-5 IMAGES

PERDAS DE SOLO NA BACIA DO RIO CEDRO/MG A PARTIR DE IMAGENS DO SENSOR TM/LANDSAT-5 Mudanças no uso e na cobertura do solo podem provocar degradação em decorrência da perda de solo proveniente do arraste das partículas, resultando no assoreamento dos rios, o que causam danos muitas vezes irreversíveis. Portanto o objetivo do trabalho foi determinar a perda de solo, por meio da Equação Universal de Perda do Solo (EUPS), na bacia do rio Cedro, norte de Minas Gerais, a partir de séries temporais de imagens de satélite LANDSAT-5/TM. Na metodologia foi inclusa a aquisição e classificação das imagens LANDSAT-5/TM para os anos de 1984, 1990, 2000 e 2011. Foram gerados mapas correspondentes aos parâmetros: erosividade, erodibilidade, grau de declive, comprimento do declive, mapa de uso e ocupação do solo e práticas conservacionistas. O mapa final de perda de solo foi elaborado no ambiente LEGAL/SPRING/versão 5.1.8 por meio da álgebra de mapas. As perdas de solo na bacia, para todos os anos, foram moderadas, para áreas mais suaves e com boa cobertura vegetal; até perda muito alta, para áreas de relevo com declividade superior a 20% e com pouca cobertura vegetal. A perda de solo para o ano de 1984 foi menor, enquanto que, para os anos de 1990 e 2000 foram registradas maiores perdas.Palavras-chave: sistema de informação geográfica, equação universal de perda de solo, degradação ambiental. ABSTRACTChanges in land use and land coverage can cause degradation due to soil loss from the drag of particles, ultimately leading to siltation of rivers and irreversible damage. Thus, the objective of this study was to determine the soil loss in the basin of the Cedro river, north of Minas Gerais, Brazil, using the Universal Soil Loss Equation (USLE) and time series of LANDSAT-5/TM satellite images. The methodology included the acquisition and classification of LANDSAT-5/TM images for the years 1984, 1990, 2000 and 2011. Maps corresponding to the following parameters were generated: erosivity; erodibility; slope degree; slope length, map of soil use and occupation and conservation practices. The final soil loss map was drawn up in the environment LEGAL/SPRING/version 5.1.8 through map algebra. Soil losses in the basin were moderate for all years in the case of areas with slight slopes and with good vegetation cover. In turn, soil loss was very high in the case of areas with slopes above 20% and with little vegetation cover. Soil loss for the year 1984 was lower, while major losses were recorded for the years 1990 and 2000.Keywords: geographic information system, universal equation of soil loss, environmental degradation. DOI: http://dx.doi.org/10.14583/2318-7670.v04n05a0

Análise da comportamento espectral da água do Rio Doce, Brasil, mediante o rompimento da barragem de sedimentos da empresa SAMARCO

A Barragem de Fundão, localizada na Bacia Hidrográfica do Rio Doce, Brasil, destinava-se ao acúmulo de sedimentos das atividades de extração de minério de ferro da empresa SAMARCO. Esta barragem rompeu-se no dia 5 de novembro de 2015, causando enorme desastre ambiental em todos os cursos d’agua à jusante, até atingir o Oceano Atlântico. A lama de rejeitos atingiu o Rio Doce e alterou a qualidade da água para captação e consumo em diversos municípios, sendo um desses o de Governador Valadares (MG). Sabe-se que, dentro das aplicações do sensoriamento remoto para a engenharia, a análise visual e do comportamento espectral dos alvos auxilia a tomada de decisão para a recuperação e o manejo de bacias hidrográficas. Desta forma, analisou-se o comportamento espectral da água e do NDWI (Normalized Difference Water Index) de seis imagens do Landsat 8 para o município de Governador Valadares, sendo duas antes e quatro após o rompimento da barragem (datas 05/08/2014; 25/09/2015; 12/11/2015, 16/02/2016; 10/08/2016 e 10/06/2017). Em escala de 0-1, o pico de reflectância da água antes ao ocorrido (05/08/2014) era da banda do verde, de 0,048. A imagem referente ao dia 12/11/2015, logo após o rompimento, apresentou maior reflectância em todas as bandas, com maior pico na infravermelho próximo (0,48), banda esta correspontente à resposta dos alvos sólidos suspensos na água e vegetação, bem como elevação do NDWI. A reflectância foi reduzida após 8 meses do desastre, entretanto em nenhuma data analisada o comportamento espectral equivaleu-se ao observado antes do desastre ambienta

Análise da comportamento espectral da água do Rio Doce, Brasil, mediante o rompimento da barragem de sedimentos da empresa SAMARCO

A Barragem de Fundão, localizada na Bacia Hidrográfica do Rio Doce, Brasil, destinava-se ao acúmulo de sedimentos das atividades de extração de minério de ferro da empresa SAMARCO. Esta barragem rompeu-se no dia 5 de novembro de 2015, causando enorme desastre ambiental em todos os cursos d’agua à jusante, até atingir o Oceano Atlântico. A lama de rejeitos atingiu o Rio Doce e alterou a qualidade da água para captação e consumo em diversos municípios, sendo um desses o de Governador Valadares (MG). Sabe-se que, dentro das aplicações do sensoriamento remoto para a engenharia, a análise visual e do comportamento espectral dos alvos auxilia a tomada de decisão para a recuperação e o manejo de bacias hidrográficas. Desta forma, analisou-se o comportamento espectral da água e do NDWI (Normalized Difference Water Index) de seis imagens do Landsat 8 para o município de Governador Valadares, sendo duas antes, e quatro após o rompimento da barragem (datas 05/08/2014; 25/09/2015; 12/11/2015, 16/02/2016; 10/08/2016 e 10/06/2017). Em escala de 0-1, o pico de reflectância da água antes ao ocorrido (05/08/2014) era da banda do verde, de 0,048. A imagem referente ao dia 12/11/2015, logo após o rompimento, apresentou maior reflectância em todas as bandas, com maior pico na infravermelho próximo (0,48), banda esta correspontente à resposta dos alvos sólidos suspensos na água e vegetação, bem como elevação do NDWI. A reflectância foi reduzida após 8 meses do desastre, entretanto em nenhuma data analisada o comportamento espectral equivaleu-se ao observado antes do desastre ambiental. &nbsp