947 resultados para Environmental effect
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Includes bibliography
Resumo:
Includes bibliography
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We investigated the effects of environmental light colors (blue, yellow and white) on the stress responses (measured by changes in ventilatory frequency - VF) of Nile tilapia to confinement. After 7 days of light treatment, the VF was similar for fish in each color. On the 8th day, fish were confined for 15. min. After release, the post-confinement VF was measured six times (first period: 0, 2 and 4. min; second period: 6, 8 and 10. min). Irrespective of the light color treatment, confinement increased the VF to higher levels during the first post-confinement period than during the second one. When color was analyzed, irrespective of time, fish under white light increased their VF post-confinement, and blue light prevented this effect. We conclude that blue light is the preferred color for Nile tilapia in terms of reducing stress. This finding is in contrast to previous choice test studies that indicated that yellow is their preferred color. © 2012 Elsevier GmbH.
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The effects of shading and water sprinkling on physiological responses and milk production were studied in Holstein cows managed in an equatorial semi-arid region. Five cows were observed for 36 days during May and June 2009. We studied the effects of sun, shade, shade plus single sprinkling, shade plus sprinkling every 2. h and shade plus sprinkling every hour on physiological responses, i.e., rectal temperature, coat surface temperature and respiratory rate, and on milk production. Environmental variables, i.e., air temperature, black globe temperature, mean radiant temperature, relative humidity and wind speed, were recorded every 30. min throughout the observation period. The statistical analysis utilized a 5×5 replicated latin square, and the results showed reduced values in physiological variables in cows that were protected from short wave radiation and that received water sprinkling; milk yield increased by approximately 3.5. kg in such animals relative to those not receiving such treatment. However, the milk yield for the morning milking presented similar mean values regardless of whether the animals received shading and sprinkling benefits, which indicates that frequency of sprinkling and amount of time (permanence) in the shade were critical for the effect on milk yield. © 2013 Elsevier B.V.
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This study aimed to estimate the acute toxicity of teflubenzuron (1-(3,5-dichloro-2,4-difluorophenyl)-3-(2,6-difluorobenzoyl)urea) (TFB) for Daphnia magna, Lemna minor and Poecilia reticulata, in the absence and presence of sediment; evaluate the effect of sediment on the TFB bioavailability; and to classify this insecticide according to its environmental poisoning risk for agricultural and aquaculture uses. The tests of TFB acute toxicity were conducted in static system in a completely randomized design with increasing TFB concentrations, and a control group. The TFB has been classified according to the estimated values of EC50 and LC50 by its acute toxicity and environmental risk. The sediment significantly reduced toxicity and bioavailability of TFB in water column. Therefore, the insecticide can be classified as being highly toxic to Daphnia magna, which means the agricultural and aquacultural uses of TFB pose a high risk of environmental toxicity to non-target organisms. However, it was practically non-toxic to L. minor and P. reticulata. © 2013 Copyright Taylor and Francis Group, LLC.
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Butyltin (BTs) quantification in environmental matrices can be affected by interfering species found primarily in complex matrices,such as sediment and biota tissues. This study investigated matrix effects in analytical procedures for butyltin (TBT,DBT and MBT) quantification and speciation in sediments and in two fish tissues (gill and liver) by gas chromatography with pulsed flame photometric detection (GC-PFPD) analysis. Unlike sediment samples,tissues exhibited a significant matrix effect,thus,the quantification should be made by curve over matrix to avoid quantification errors and loss of analytical accuracy. © 2013 Sociedade Brasileira de Química.
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The objective of this study was to evaluate the effect of betaine in methionine- and choline-reduced diets fed to broilers submitted to heat stress. In total, 1,408 male broilers were randomly distributed into eight treatments, according to 2 × 4 (environment x diet) factorial arrangement, with eight replicates of 2 birds each. Birds were reared environmental chambers under controlled temperature (25-26 °C) or cyclic heat-stressing temperature (25-31 °C). The following diets were tested: positive control (PC), formulated to meet broiler nutritional requirements; negative control (NC), with reduced DL-methionine and choline chloride levels; and with two supplementation levels of natural betaine to the negative control diet (NC+NB1 and NC+NB2). Live performance, carcass traits, and intestinal morphometrics were evaluated when broilers were 45 days of age. The results showed that all evaluated parameters were influenced by the interaction between environment and diet, except for breast meat drip loss. The breakdown of the interactions showed that birds fed the PC diet and reared in the controlled environment had greater breast drip loss than those submitted to the cyclic heat-stress environment. Birds submitted to cyclic heat stress and fed the PC diet presented the lowest feed intake. Feed conversion ratio was influenced only by diet. The FCR of broilers fed the NC+NB2 diet was intermediate relative to those fed the PC and NC diets. The addition of betaine in the diet, with 11.18% digestible methionine and 24.73% total choline reductions, did not affect broiler live performance, carcass yield, or intestinal morphometrics.
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Cellulose micro and nano fibrils were extracted from banana macro fibres and chemically modified using sodium hydroxide, formic acid, 3-methacryloxy propyltrimethoxy silane. These untreated and chemically treated fibrils were incorporated into PF resin and the specimens were prepared. The composites were subjected to long-term water ageing, thermal ageing soil burial and outdoor weathering. The mechanical properties are reduced under all ageing conditions. The present study investigates the effects of different types of ageing on macro fibre, microfibril and nanofibril reinforced PF composites. The effect of chemical modifications of fibres on the degradability of the composites at different environments also has been analysed. © 2013 Elsevier B.V.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Foi realizado um estudo sobre a estrutura das comunidades planctônicas ao longo das praias de Casa Caiada e Rio Doce (Pernanbuco, Brasil). A área de estudo sofre grande influência antrópica onde as condições ambientais são controladas pela presença de estruturas costeiras, reduzindo a intensidade da circulação neste ambiente; e pelos efluentes clandestinos de esgoto que aportam águas poluídas para dentro do sistema protegido. Os resultados obtidos indicam que nas zonas protegidas as águas apresentam alta turbidez, temperaturas elevadas, salinidades reduzidas e altas concentrações de nutrientes e oxigênio. Estas condições são responsáveis pela redução da diversidade do plâncton e pelo aumento da biomassa das espécies mais resistentes. As diferenças registradas com respeito a áreas similares, porém não impactadas, parecem indicar que a estrutura planctônica pode ser usada como um indicador da qualidade ambiental, sugerindo uma baixa qualidade das praias em estudo.
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Because an enriched environment (EE) enhances T-cell activity and T-lymphocytes contribute to immunopathogenesis during heterologous dengue virus (DENV) infections, we hypothesised that an EE increases dengue severity. To compare single serotype (SS) and antibody-enhanced disease (AED) infections regimens, serial intraperitoneal were performed with DENV3 (genotype III) infected brain homogenate or anti-DENV2 hyperimmune serum followed 24 h later by DENV3 (genotype III) infected brain homogenate. Compared AED for which significant differences were detected between the EE and impoverished environmental (IE) groups (Kaplan-Meyer log-rank test, p = 0.0025), no significant differences were detected between the SS experimental groups (Kaplan-Meyer log-rank test, p = 0.089). Survival curves from EE and IE animals infected with the AED regimen were extended after corticoid injection and this effect was greater in the EE than in the IE group (Kaplan-Meyer log-rank test, p = 0.0162). Under the AED regimen the EE group showed more intense clinical signs than the IE group. Dyspnoea, tremor, hunched posture, ruffled fur, immobility, pre-terminal paralysis, shock and death were associated with dominant T-lymphocytic hyperplasia and presence of viral antigens in the liver and lungs. We propose that the increased expansion of these memory T-cells and serotype cross-reactive antibodies facilitates the infection of these cells by DENV and that these events correlate with disease severity in an EE.
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Características ambientais e distâncias espaciais entre os locais foram utilizadas para explicar a distribuição das espécies no ambiente, através das predições da teoria Neutra (espaço) e teoria do Nicho (ambiente). Foram avaliados os efeitos de fatores geográficos e ambientais sobre a distribuição de larvas de Odonata ao longo da Bacia do Rio Suiá-Missu, no estado de Mato Grosso. Nós testamos a hipótese de que (1) o ambiente é o principal fator de estruturação da comunidade devido às suas exigências ecofisiológicas; e (2) o padrão, se presente, é mais expressivo para Zygoptera. As amostras foram feitas em 12 locais na Bacia do Rio Suiá-Missu, em três campanhas (2007/2008), com um total de 1.382 larvas de Odonata, composta por 10 famílias, 51 gêneros e 100 morfoespécies. Os Anisoptera foram mais abundantes que Zygoptera, que compreende 81% de todas as amostras. O ambiente afetou Zygoptera (R = 0,291; p = 0,007) e foi o principal fator de estruturação da assembléia. Assim, a teoria do nicho foi confirmada. A ausência deste efeito sobre Anisoptera pode ser devido às adaptações ecofisiológicos que lhes permitem ocupar diferentes habitats. Larvas de Zygoptera são indicadores de mudanças na estrutura do habitat. Os efeitos das variáveis ambientais sobre a ecologia das larvas enfatizam a forte relação entre esses organismos e integridade ambiental.
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Each year, there is an increase in pesticide consumption and in its importance of use in the large-scale agricultural production, being fundamental the knowledge of application technology to the activity success. The objective of the present study was to evaluate the influence of working pressure on the drift generated by different spray nozzles, assessed in wind tunnel. The treatments were composed of two spray nozzles AXI 110015 and AXI 11002 with pressure levels of 276 and 414 kPa. The spray solution was composed by water and NaCl at 10%. The applications were conducted at wind speed of 2.0 m s-1, being the drift collected at 5.0; 10.0 and 15.0 m away from the spray boom and at heights of 0.2; 0.4; 0.6; 0.8 e 1.0 m from the tunnel floor. To both spray nozzles, the greatest drift was collected at the smallest distance to the spray-boom and at the lowest height. The AXI 11002 nozzle gave a smaller drift relative to the AXI 110015 nozzle for the two tested pressures and for all the collection points. Regardless of the nozzle, a rise in the working pressure increases the spray drift percentage at all distances in the wind tunnel.
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The outdoor cultivation (ditches) of Agaricus blazei was evaluated in the protected natural area (APA) of the mountainous region of Baturité on three types of casing soils (A, B and C). Casing soil A (horizon A) of the local soil was used (Alfisol). Casing B was obtained with a mixture of 30% of eucalyptus charcoal (1-2 cm of length) and 70% of horizon B of the local soil. Casing C was composed of 25% of vermiculite, 25% of coconut fiber and 50% of coarse sand. Temperature, relative humidity and pluviometric rates were monitored. The physical-chemical properties of the three casing soils were analyzed. The effect of the casing soil on the number and weight of the mushrooms, productivity, yield and biological efficiency of A. blazei were evaluated. The yield, productivity, biological efficiency and number of mushrooms were higher when using soil A. The highest productivity for soil A was attributed mainly to the physical characteristics, which were considered more appropriate for the cultivation, in addition to the high pluviometric rates and relative humidity. The productivity with soil A (9.62%) is comparable with the average productivity obtained in Brazil, meaning that the cultivation of A. blazei in this APA may have good perspectives for cultivation.
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The present study was conducted to evaluate the effects of feeding whole linseed on the laying performance and egg characteristics in laying hens kept at high ambient environmental temperatures (average 34 degrees C; the diurnal temperature range 26 degrees C to 41 degrees C). Two hundred and forty 38-wk-old white Leghorn laying hens were fed diets containing 0, 5, 10 or 15% whole linseed (as a source of n-3 polyunsaturated fatty acids) for a period of 12 weeks. Egg production was recorded daily, while feed intake and egg characteristics were monitored on weekly basis. The results of the study demonstrated that egg production and feed intake decreased, while feed conversion ratio (FCR) per dozen of eggs increased (p <= 0.05) with increasing dietary linseed levels. Egg weight, yolk weight, albumen height, eggshell weight, and eggshell thickness were not influenced (p > 0.05) by linseed levels in the diets offered to the laying hens. The results of the present trial suggest that feeding linseed to the laying hens in hot climates has no detrimental effects on egg characteristics, but has suppressive effects on egg production, feed intake and feed efficiency of laying hens.