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Achieving sustainability in life involves increasing efforts to recover resources. This research proposes the recovery of Zn from the Milluni lagoons, an important water supply for Bolivia, where high concentrations of Zn have been identified that exceed permitted limits, exposing a risk to health and ecosystems. The application of reverse osmosis (RO), operated with low pressures, is proposed as a first stage for the concentration of Zn and subsequent recovery of this metal through chemical precipitation. The aim was to maintain the separation efficiency of the RO operated at low pressures without presenting operational problems. As a result, 98.83% metal concentration was achieved with a laboratory-scale pilot system. The above means an important potential for large-scale Zn concentration, apart from orienting the RO toward sustainability by working with low pressures that reduce energy costs during its operation. This study can be used as a valuable reference for the advancement of sustainable technologies in the field of water treatment that simultaneously allow the recovery of resources to promote a circular economy. Finally, this study exposes an alternative for regions with heavy metal water contamination in Bolivia and worldwide.

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The food and beverage industries in Mexico generate substantial effluents, including nejayote, cheese-whey, and tequila vinasses, which pose significant environmental challenges due to their extreme physicochemical characteristics and excessive organic load. This study aimed to assess the potential of Chlorella vulgaris in bioremediating these complex wastewaters while also producing added-value compounds. A UV mutagenesis treatment (40 min) enhanced C. vulgaris adaptability to grow in the effluent conditions. Robust growth was observed in all three effluents, with nejayote identified as the optimal medium. Physicochemical measurements conducted pre- and post-cultivation revealed notable reductions of pollutants in nejayote, including complete removal of nitrogen and phosphates, and an 85 % reduction in COD. Tequila vinasses exhibited promise with a 66 % reduction in nitrogen and a 70 % reduction in COD, while cheese-whey showed a 17 % reduction in phosphates. Regarding valuable compounds, nejayote yielded the highest pigment (1.62 mg·g-1) and phenolic compound (3.67 mg·g-1) content, while tequila vinasses had the highest protein content (16.83 %). The main highlight of this study is that C. vulgaris successfully grew in 100 % of the three effluents (without additional water or nutrients), demonstrating its potential for sustainable bioremediation and added-value compound production. When grown in 100 % of the effluents, they become a sustainable option since they don't require an input of fresh water and therefore do not contribute to water scarcity. These findings offer a practical solution for addressing environmental challenges in the food and beverage industries within a circular economy framework.

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Phycocyanin is a highly valued pigment present in Spirulina platensis biomass with applications in the food industry in terms of biorefinery concepts; specifically, its antioxidant and antimicrobial capacity are an advantage that could be incorporated into a food matrix. This study aims to use rice husk as an alternative culture medium for S. platensis biomass growth and phycocyanin extraction by ohmic heating processing using a 3D-printed reactor. S. platensis was cultivated in rice husk extract (RHE) from 0-100% (v/v). The highest content of microalgal biomass was 1.75 ± 0.01 g/L, with a specific growth rate of 0.125 ± 0.01 h-1. For the phycocyanin extraction under an ohmic heating process, a 3D-printed reactor was designed and built. To optimize phycocyanin extraction, a central composite rotatable design (CCDR) was evaluated, with three factors: time (min), temperature (°C), and pH. The highest phycocyanin content was 75.80 ± 0.98 mg/g in S. platensis biomass grown with rice husk extract. Ohmic heating is a promising method for rapid phycocyanin extraction, and rice husk as a culture medium is an alternative for the growth of S. platensis biomass in the integration of second- and third-generation biorefineries.

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The reuse and reincorporation of waste are the principles of circular economies. Compost, biofuels, animal feed, dyes, and bioactive compounds can be obtained from the revaluation of organic waste. Research on this subject is scarce and limited to specific sectors, such as agriculture and agroindustry, leaving aside others that generate large quantities of organic waste, such as floriculture. The remains of these sectors have a low decomposition rate compared to other organic wastes. They are a source of bioactive compounds (e.g., essential oils, pigments, phenols) that can be reincorporated into the production chain of various industries. This review describes the composition of waste from agroindustry, agriculture, and floriculture, analyzing their potential revalorization as a source of bioactive compounds and an alternative supply source.

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In the context of a biorefinery, lignocellulosic materials represent an important source of raw material for the bioconversion of cellulose, hemicellulose, and lignin into value-added products, such as xylose for fermentation, oligosaccharides, and bioplastics for packaging. Among the most abundant lignocellulosic materials in Brazil, sugarcane bagasse biomass stands out, as it is rich in cellulose and hemicellulose. In this context, through an experimental design, this study developed a robust enzyme cocktail containing xylanases and accessory enzymes to complete the hydrolysis of xylan from sugarcane bagasse, obtaining a low xylose yield and concentration (9% and 1.8 g/L, respectively, observed in experiment number 16 from the complete hydrolysis of a xylan assay), a fermentable sugar that is important in the production of second-generation ethanol, and a high xylooligosaccharides (XOS) yield and concentration (93.1% and 19.6 g/L, respectively, obtained from a xylooligosaccharides production assay); in general, xylan has prebiotic activities that favor an improvement in intestinal functions, with immunological and antimicrobial actions and other benefits to human health. In addition to completely hydrolyzing the sugarcane bagasse xylan, this enzymatic cocktail has great potential to be applied in other sources of lignocellulosic biomass for the conversion of xylan into xylose and XOS due to its enzymes content, involving both main chain and pendant groups hydrolysis of hemicelluloses.

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The lignocellulose biorefinery industry has assumed an important role within the current scenario. Lignin is an abundant and available biopolymer and one of the compounds present in the lignocellulosic waste. Therefore, processing lignin into new materials and nanomaterials, such as nanolignin, has attracted the attention of the scientific community. Lignin nanoparticles are materials that have excellent properties, such as biodegradability and non-toxicity, and have great potential as chelating agents, antimicrobials agents, UV protectors, nanofillers, adsorbents, catalysts, supercapacitors, emulsion stabilizers, delivered systems, drugs, and gene carriers. This review article covers the emergent scenario of nanolignin and the main aspects of scientific interest, such as the conversion and functionalization of lignin, the valorization of lignocellulose waste, and nanoparticle synthesis. A techno-economic evaluation of the biorefinery model of the nanolignin synthesis is presented based on the simulation of the process on the experimental and commercial databases available and reported by some authors. Finally, the techno-economic assessment is complemented by the life cycle assessment of various nanolignin synthesis pathways reported to evaluate the environmental implications and support this emergent technology development.

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Aqueous and ethanolic pomegranate peel extracts (PPE) were studied as a source of phenolic compounds with antimicrobial, anti-quorum sensing, and antioxidant properties. The aqueous extract showed higher total phenolic and flavonoid content (153.43 mg GAE/g and 45.74, respectively) and antioxidant capacity (DPPH radical inhibition: 86.12%, ABTS radical scavenging capacity: 958.21 mg TE/dw) compared to the ethanolic extract. The main phenolic compounds identified by UPLC-DAD were chlorogenic and gallic acids. The aqueous PPE extract showed antimicrobial activity against Listeria monocytogenes, Salmonella Typhimurium, Candida tropicalis (MICs 19-30 mg/mL), and anti-quorum sensing activity expressed as inhibition of Chromobacterium violaceum violacein production (%). The aqueous PPE extracts at 25 mg/mL applied on alfalfa sprouts reduced psychrophilic bacteria (1.12 Log CFU/100 g) and total coliforms (1.23 Log CFU/100 g) and increased the antioxidant capacity of the treated sprouts (55.13 µmol TE/100 g (DPPH) and 126.56 µmol TE/100 g (ABTS)) compared to untreated alfalfa. This study emphasizes PPE's antioxidant and antimicrobial activities in alfalfa sprouts preservation.

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Agave lechuguilla agro-waste is a promising renewable material for biorefining purposes. The procurement of added-value co-products, such as bioactive phytochemicals, is required to improve bioprocesses and promote the bio-based economy of the productive areas of Mexico. In this study, we aimed to evaluate the effect of post-harvest management and enzymatic pretreatment as the first stages of the A. lechuguilla valorization process. Four drying methods were compared, and enzymatic hydrolysis was optimized to obtain a flavonoid-enriched extract applying ultrasound-assisted extraction. In both experiments, the total phenolic (TPC) and flavonoid (TFC) contents, HPLC-UV flavonoid profiles, and radical scavenging capacity (DPPH) were considered as response variables. The results demonstrated that light exposure during the drying process particularly affected the flavonoid content, whereas oven-dehydration at 40 °C in the dark preserved the flavonoid diversity and antioxidant functionality of the extracts. Flavonoid glycoside recovery, particularly anthocyanidins, was 1.5-1.4-fold enhanced by enzymatic hydrolysis using the commercial mix Ultraflo© under optimized conditions (pH 4, 40 °C, 180 rpm, and 2.5 h) compared to the unpretreated biomass. The extraction of flavonoids from A. lechuguilla bagasse can be carried out using a scalable drying method and enzymatic pretreatment. This study confirmed the potential of this agro-waste as a source of marketable natural products.

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This study aimed to analyze the quality of and differences between mechanically separated meat (MSM) and surimi obtained from red porgy (Pagrus pagrus) and Brazilian flathead (Percophis brasiliensis) fish caught in the “mixed” trawl category at Niterói, Rio de Janeiro, Brazil. The surimi was produced from the MSM of both fish species subjected to washing. The chemical characterization of the products was carried out by chemical composition analyses (moisture, protein, lipids and ash content). Microbiological analyses, namely coagulase positive staphylococci, coliforms at 35 ° C, thermotolerant coliforms and Salmonella sp. counts, were performed. Surimi produced from red porgy and Brazilian flathead presented lower protein (7.84% and 7.34%) and lipid (0.73% and 0.74%) content and higher moisture content (91.71% and 90.15%), respectively, compared to MSM (P <0.05). The microbiological analyses indicated that the products were within the sanitary standards required by Brazilian legislation. In sum, the low added value fish from the “mix” category resulted in viable products (MSM and surimi) for use in fish technology. The MSM product exhibited higher nutritional richness than surimi, but with a higher bacterial load.

Este estudo teve como objetivo analisar a qualidade e as diferenças entre a carne mecanicamente separada (CMS) e surimi obtidos a partir de pargo (Pagrus pagrus) e o tira-vira (Percophis brasiliensis) capturados na categoria “mistura” da modalidade da pesca de arrasto de Niterói, RJ. Para elaboração do surimi, as CMS de pargo e tira-vira foram submetidas à lavagem. A caracterização química dos produtos foi determinada pelas análises da composição química (umidade, proteína, lipídeos e cinzas). Para as análises microbiológicas foram realizadas contagens de Estafilococos coagulase positiva, coliformes a 35 °C, coliformes termotolerantes e pesquisa de Salmonella sp. Os surimis de pargo e tira-vira apresentaram menores teores proteico (7,84% e 7,34%) e lipídico (0,73% e 0,74%) e maior umidade (91,71% e 90,15%), respectivamente, em comparação à CMS (P<0,05). A análise microbiológica demonstrou que os produtos estavam dentro do padrão sanitário exigido pela legislação. Com base nos resultados obtidos, conclui-se que os peixes de baixo valor agregado da categoria “mistura” resultaram em produtos (CMS e surimi) viáveis para o uso na tecnologia do pescado. O produto CMS apresentou-se mais rico nutricionalmente do que o surimi, porém com maior carga bacteriana.

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This study aimed to analyze the quality of and differences between mechanically separated meat (MSM) and surimi obtained from red porgy (Pagrus pagrus) and Brazilian flathead (Percophis brasiliensis) fish caught in the “mixed” trawl category at Niterói, Rio de Janeiro, Brazil. The surimi was produced from the MSM of both fish species subjected to washing. The chemical characterization of the products was carried out by chemical composition analyses (moisture, protein, lipids and ash content). Microbiological analyses, namely coagulase positive staphylococci, coliforms at 35 ° C, thermotolerant coliforms and Salmonella sp. counts, were performed. Surimi produced from red porgy and Brazilian flathead presented lower protein (7.84% and 7.34%) and lipid (0.73% and 0.74%) content and higher moisture content (91.71% and 90.15%), respectively, compared to MSM (P <0.05). The microbiological analyses indicated that the products were within the sanitary standards required by Brazilian legislation. In sum, the low added value fish from the “mix” category resulted in viable products (MSM and surimi) for use in fish technology. The MSM product exhibited higher nutritional richness than surimi, but with a higher bacterial load.(AU)

Este estudo teve como objetivo analisar a qualidade e as diferenças entre a carne mecanicamente separada (CMS) e surimi obtidos a partir de pargo (Pagrus pagrus) e o tira-vira (Percophis brasiliensis) capturados na categoria “mistura” da modalidade da pesca de arrasto de Niterói, RJ. Para elaboração do surimi, as CMS de pargo e tira-vira foram submetidas à lavagem. A caracterização química dos produtos foi determinada pelas análises da composição química (umidade, proteína, lipídeos e cinzas). Para as análises microbiológicas foram realizadas contagens de Estafilococos coagulase positiva, coliformes a 35 °C, coliformes termotolerantes e pesquisa de Salmonella sp. Os surimis de pargo e tira-vira apresentaram menores teores proteico (7,84% e 7,34%) e lipídico (0,73% e 0,74%) e maior umidade (91,71% e 90,15%), respectivamente, em comparação à CMS (P<0,05). A análise microbiológica demonstrou que os produtos estavam dentro do padrão sanitário exigido pela legislação. Com base nos resultados obtidos, conclui-se que os peixes de baixo valor agregado da categoria “mistura” resultaram em produtos (CMS e surimi) viáveis para o uso na tecnologia do pescado. O produto CMS apresentou-se mais rico nutricionalmente do que o surimi, porém com maior carga bacteriana.(AU)

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The demand for beef cattle with specific traits is evident from sales in auctions. While purchasing, buyers consider individual traits (e.g., muscularity, frame, racial composition, and weight) as predictors of quality, and adjust their bids according to their preferences. The present study aimed to evaluate the effect of phenotypic and racial characteristics in determining the final sale price of calves of beef cattle in official auctions at the western border of the state of Rio Grande do Sul, Brazil. Five-hundred and seven lots of calves sold in calf auctions from five cities on the western border of Rio Grande do Sul were evaluated. The assignment of visual scores was based on their genetic group, frame, muscularity, and coat. Analysis of variance and the Tukey test at 5% significance level were performed for comparing the final average prices. Variables with the greatest impact on price were the genetic group and the size of the animals. Animals of synthetic breeds obtained higher value in the three years studied and animals without racial definition showed considerable devaluation and a decrease in supply. Larger animals had less value.(AU)

A busca por animais com características específicas é evidenciada na comercialização em leilões, em que, ao analisar os animais, compradores consideram as características individuais (musculosidade, frame, composição racial, peso) como preditor de qualidade e ajustam seus lances conforme suas preferências. Dessa forma, o presente estudo buscou avaliar o impacto de características fenotípicas e de padrão racial na composição do preço final de venda de bezerros comercializados em feiras oficiais na fronteira oeste do Rio Grande do Sul. Foram avaliados 507 lotes de bezerros comercializados nas feiras de terneiros de cinco municípios da região da Fronteira Oeste do estado do Rio Grande do Sul. Para a atribuição de escores visuais, considerou-se grupo genético, frame, musculosidade e pelagem dos animais. Foi realizada a análise de variância e a comparação dos preços finais médios pelo teste de Tukey a 5% de significância. As variáveis de maior impacto no preço foram grupo genético e tamanho dos animais. Animais de raças sintéticas obtiveram valorização superior nos três anos Estudados, considerável desvalorização e queda na oferta de animais sem definição racial. Os menores valores foram atribuídos a animais de tamanho grande.(AU)

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ABSTRACT: The demand for beef cattle with specific traits is evident from sales in auctions. While purchasing, buyers consider individual traits (e.g., muscularity, frame, racial composition, and weight) as predictors of quality, and adjust their bids according to their preferences. The present study aimed to evaluate the effect of phenotypic and racial characteristics in determining the final sale price of calves of beef cattle in official auctions at the western border of the state of Rio Grande do Sul, Brazil. Five-hundred and seven lots of calves sold in calf auctions from five cities on the western border of Rio Grande do Sul were evaluated. The assignment of visual scores was based on their genetic group, frame, muscularity, and coat. Analysis of variance and the Tukey test at 5% significance level were performed for comparing the final average prices. Variables with the greatest impact on price were the genetic group and the size of the animals. Animals of synthetic breeds obtained higher value in the three years studied and animals without racial definition showed considerable devaluation and a decrease in supply. Larger animals had less value.

RESUMO: A busca por animais com características específicas é evidenciada na comercialização em leilões, em que, ao analisar os animais, compradores consideram as características individuais (musculosidade, frame, composição racial, peso) como preditor de qualidade e ajustam seus lances conforme suas preferências. Dessa forma, o presente estudo buscou avaliar o impacto de características fenotípicas e de padrão racial na composição do preço final de venda de bezerros comercializados em feiras oficiais na fronteira oeste do Rio Grande do Sul. Foram avaliados 507 lotes de bezerros comercializados nas feiras de terneiros de cinco municípios da região da Fronteira Oeste do estado do Rio Grande do Sul. Para a atribuição de escores visuais, considerou-se grupo genético, frame, musculosidade e pelagem dos animais. Foi realizada a análise de variância e a comparação dos preços finais médios pelo teste de Tukey a 5% de significância. As variáveis de maior impacto no preço foram grupo genético e tamanho dos animais. Animais de raças sintéticas obtiveram valorização superior nos três anos Estudados, considerável desvalorização e queda na oferta de animais sem definição racial. Os menores valores foram atribuídos a animais de tamanho grande.

RESUMO

The demand for beef cattle with specific traits is evident from sales in auctions. While purchasing, buyers consider individual traits (e.g., muscularity, frame, racial composition, and weight) as predictors of quality, and adjust their bids according to their preferences. The present study aimed to evaluate the effect of phenotypic and racial characteristics in determining the final sale price of calves of beef cattle in official auctions at the western border of the state of Rio Grande do Sul, Brazil. Five-hundred and seven lots of calves sold in calf auctions from five cities on the western border of Rio Grande do Sul were evaluated. The assignment of visual scores was based on their genetic group, frame, muscularity, and coat. Analysis of variance and the Tukey test at 5% significance level were performed for comparing the final average prices. Variables with the greatest impact on price were the genetic group and the size of the animals. Animals of synthetic breeds obtained higher value in the three years studied and animals without racial definition showed considerable devaluation and a decrease in supply. Larger animals had less value.

A busca por animais com características específicas é evidenciada na comercialização em leilões, em que, ao analisar os animais, compradores consideram as características individuais (musculosidade, frame, composição racial, peso) como preditor de qualidade e ajustam seus lances conforme suas preferências. Dessa forma, o presente estudo buscou avaliar o impacto de características fenotípicas e de padrão racial na composição do preço final de venda de bezerros comercializados em feiras oficiais na fronteira oeste do Rio Grande do Sul. Foram avaliados 507 lotes de bezerros comercializados nas feiras de terneiros de cinco municípios da região da Fronteira Oeste do estado do Rio Grande do Sul. Para a atribuição de escores visuais, considerou-se grupo genético, frame, musculosidade e pelagem dos animais. Foi realizada a análise de variância e a comparação dos preços finais médios pelo teste de Tukey a 5% de significância. As variáveis de maior impacto no preço foram grupo genético e tamanho dos animais. Animais de raças sintéticas obtiveram valorização superior nos três anos Estudados, considerável desvalorização e queda na oferta de animais sem definição racial. Os menores valores foram atribuídos a animais de tamanho grande.

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Plastic waste from electrical and electronic equipment (WEEE) grows up exponentially fast in the last two decades. Either consumption increase of technological products, like cellphones or computers, or the short lifetime of this products contributes to this rise generating an accumulation of specific plastic materials such ABS (Acrylonitrile-Butadiene-Styrene), HIPS (High impact Polystyrene), PC (Polycarbonate), among others. All of they can be recycled by themselves. However, to separate them by type is neither easy nor economically viable, then an alternative is recycling them together as a blend. Taking into account that could be a deterioration in final properties, to enhance phase adhesion and add value to a new plastic WEEE blend a compatibilization is needed. In this work, a systematical study of different compatibilizers for blends of HIPS and ABS from WEEE was performed. A screening analysis was carried out by adding two different compatibilizer concentration (2wt% and 20wt%) on a HIPS/ABS physical blend 80/20 proportion from plastic e-waste. Three copolymers were selected as possible compatibilizers by their possible affinity with initial plastic WEEE. A complete characterization of each WEEE was performed and compatibilization efficiency was evaluated by comparing either mechanical or morphological blends aspects. Considering blends analyzed in this work, the best performance was achieved by using 2% of styrene-acrylonitrile rubber, obtaining a compatibilized blend with double ultimate strength and modulus respect to the physical blend, and also improve mechanical properties of initial WEEE plastics. The proposed way is a promise route to improve benefit of e-scrap with sustainable, low costs and easy handling process. Consequently, social recycling interest will be encouraged by both ecological and economical points of view.

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Socioeconomic activities and their gross income in Isla del Coco National Park have been poorly evaluated and systematized, as well as the effects on them climate variability may have. A methodology that combines cluster analysis with a dynamic value chain was developed to identify the most important socioeconomic activities and quantify the gross income derived by the existence of Isla del Coco National Park. The possible effects of climate variability on these activities were also analyzed. A detailed literature review, consultation and interviews with researchers, entrepreneurs and tourists were conducted in order to apply the methodology. The main clusters of activities around this park are leisure and spiritual experiences, research and education, economic activities and park management. An approximation of the gross income from the activities carried out around the National Park in 2010 was calculated. The gross income generated at the national level was $5.7 million dollars and at the international level was $2.5 million dollars. The overall gross income was approximately $8.3 million dollars. But, if the natural resources being visited by tourists degrade due to the effects of climate variability these benefits could decrease by 30%.

Las actividades socioeconómicas y sus ingresos en el Parque Nacional Isla del Coco han sido poco evaluados y sistematizados, al igual que los efectos que sobre ellos pueda tener la variabilidad climática. empleó una metodología que combina análisis de conglomerados con una dinámica de valor agregado en una cadena productiva, para identificar las actividades socioeconómicas más importantes y cuantificar los ingresos que obtienen por la existencia del PNIC, además se analizó los posibles efectos de la variabilidad climática sobre estas actividades. Para lo anterior, se realizó una revisión bibliográfica detallada, consulta con empresarios, investigadores y turistas. Se obtuvo que los principales conglomerados de actividades alrededor del PNIC son la recreación y la vivencia espiritual, la investigación, las actividades económicas y la gestión y manejo del Parque. Se realizó una aproximación de las contribuciones de la existencia del PNIC en estos cuatro conglomerados en el 2010, y se obtuvo que la contribución el ámbito nacional fue de US$5.7 millones de dólares, el internacional de US$2.5 millones de dólares, el global del PNIC ascendió aproximadamente a US$8.3 millones de dólares. También se obtuvo que si los recursos naturales objeto de la visita de los turistas disminuyen debido a efectos de la variabilidad climática esto ingresos podrían disminuir en 30%.

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Sorgo, milho, milhetos, aveia preta, trigo, cevada, braquiária, nabo forrageiro, amaranto, quinoa, kenaf, gergelim, girassol, girassol selvagem, guandu e Crotalaria spectabilis, foram avaliados após o cultivo de primavera-verão e na entressafra, irrigada, no Cerrado do Planalto Central. O estudo objetivou a produção de biomassa com implicações na proteção e manejo do solo, aporte de forragem, grãos e outras matérias-primas com valor agregado. Os experimentos foram conduzidos em três locais, no delineamento de blocos ao acaso, com genótipos previamente selecionados. As comparações se basearam nos seguintes parâmetros: ciclo (número de dias entre emergência e maturação), altura de plantas e produção de grãos e de biomassa. A diferença entre os dois locais pode ser atribuída às variações na fertilidade do solo. Algumas espécies mostraram maior estabilidade, como Brachiaria brizantha, sorgo, milheto e kenaf. O crescimento e a produção de biomassa não mostra efeito de fotoperíodo, exceto para gergelim. Os resultados indicam potencial de agregação de valor a espécies pouco exploradas na agricultura brasileira como amaranto, quinoa e kenaf.

Agronomic performance of sorghum, millets, maize, black oats, wheat, barley, brachiaria grass, forage turnip, grain amaranth, quinoa, kenaf, sesame, sunflower, wild sunflower, pigeon pea and Crotalaria spectabilis was evaluated in sowings after summer cropping and winter, under irrigation in the Brazilian Savannah high lands. The study aimed at biomass production with impacts on soil protection and management, and source of forage, added value grains and raw material. Experiments in complete randomized blocks were conducted at three locations, with previously selected genotypes. Evaluations were based on the following parameters: plant cycle (number of days between emergence and maturity), plant height, biomass production and grain yield. Some species showed more yield stability, such as Brachiaria brizantha, sorghum, pearl millet and kenaf, and the difference for the two locations may be related to soil fertility. Plant growth and biomass production showed no effect of photoperiod, except for sesame. Grain yield indicates the potential for added value in less exploited crops for the Brazilian agriculture, such as quinoa and grain amaranth

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RESUMO

En el estudio que se informa se investigaron las relaciones entre progreso de aprendizaje (valor agregado), motivación y autoconcepto académico del alumno en Matemática, en el marco de los efectos de las características socioeconómicas y académicas del alumno y de su escuela. Para la medición del valor agregado se utilizaron los resultados de dos pruebas estandarizadas de Matemática aplicadas a una cohorte de alumnos de la Provincia de Buenos Aires (República Argentina) en dos momentos diferentes (séptimo y noveno años de Educación General Básica - EGB). Las mediciones de motivación y de autoconcepto se basaron en respuestas a ítemes binarios de actitudes con respecto a Matemática y fueron definidas utilizando el análisis de la componente principal, a partir de la matriz de correlación tetracórica (método heurístico). Para el análisis de las correlaciones se utilizó la técnica estadística de modelos multinivel. El presente estudio relaciona los resultados empíricos con la teoría del habitus de Bourdieu. Inicialmente, el autoconcepto resulta significativa y positivamente asociado con el puntaje en la prueba y con el progreso de aprendizaje posterior. Este efecto continúa siendo significativo aun cuando se controlan los efectos del nivel socioeconómico y del género del alumno. Sin embargo, su capacidad explicativa es muy tenue desde el punto de vista práctico. Si bien este resultado confirmaría la hipótesis central de la teoría de la reproducción, indica un sendero a través del cual podrían producirse transformaciones. Uno de los desafíos del sistema educativo es promover el habitus escolar cultivado (autoconcepto) más allá de las determinaciones sociales, culturales y económicas.

The project examines the relationship between achievement, motivation and academic self-concept connected to Mathematic, related to the effect of academic and socioeconomic characteristics of both student and school. The study analyzes the results of two standardized Mathematic tests applied to students in General Basic Education of the Province of Buenos Aires (República Argentina) at two different stages (7th and 9th years), adopting the added value approach to learning progress. The structure of the data and the purpose of measuring the contextual effect of each school or group of students require adopting a multi-level strategy for statistical analysis. From a theoretical point of view, this study is an empirical proof of the hypothesis on habitus-determination (Bourdieu, 1977, 1988, 1989) in relation to both achievement and learning progress in Mathematic. The main components of the student's habitus, which are analyzed here, are self-concept and academic motivation. One relevant result of this study is that students' academic self-concept is significantly and positively associated to differences in learning achievement among students and schools. The higher the self-concept, the higher the achievement in Mathematic. Inter-school variations reflect the grade of institutional segmentation or school habitus. As to attitudes towards Mathematics at the initial stage (7th year) it was possible to explain 65.4% and 24.3% of the variation intra-school and inter-school, respectively, in the final academic achievement or learning progress at the final stage (9th year). Although the effect of self-concept overlaps with that of socioeconomic level and gender, its incidence is important. The stronger that attitude is, the stronger the progress of the student's later learning. The rate of students' progress increases with a more favourable social origin or male gender. The contextual analysis also allowed contrasting some hypothesis of this field of study. The initial achievement average (7th year) of students impacts positively on their subsequent progress average: the higher their initial level of achievement, the faster their later progress. This inference, however, did not obtain when the socioeconomic context of the school was included in the analysis. These results confirm the central hypotheses of reproduction theory. Although statistically significant, the characteristic effect of individual self-concept upon academic achievement and learning progress is very weak when students' social origin is taken into account. The school doesn't seem to promote the increase of individual deviations from a certain state of probabilities that are objectively granted by society to the student. The school aggregation of individual habitus merely overlaps and accompanies the explanation provided by the socioeconomic composition of the school. Differences in internal institutional processes of schools influenced by various dimensions, such as curricular goals, an organizational style of management, the culture and capabilities of educators and administrators, if they exist, cannot account for the differences and inequalities in the learning progress of students. Results illustrate the rationality of the educational system in secondary basic education. At the same time, they suggest paths whereby transformations could take place. Aspects of the cultivated habitus, affective or non-cognitive dimensions as academic self-concept, are relevant to understand the level of achievement and learning progress. The challenge for the system of education is to promote them beyond social, cultural and economic factors.