Mechanical and Thermal Characterization of Natural Intralaminar Hybrid Composites Based on Sisal.

The main objective of this work was to investigate the effect of hybridization on the mechanical and thermal properties of intralaminar natural fiber-reinforced hybrid composites based on sisal. Ramie, sisal and curauá fibers were selected as natural fiber reinforcements for the epoxy matrix based composites, which were produced by the hand lay-up technique. Tensile, flexural and impact tests were carried out according to American society for testing and materials (ASTM) standards to characterize the hybrid composites, while differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to evaluate the thermal properties. It was found that the mechanical properties are improved by hybridization of sisal based composites. The thermal analysis showed that the hybridization did not significantly affect the thermal stability of the composites. A scanning electron microscopy (SEM) was used to examine the fracture surface of the tested specimens. The SEM images showed a brittle fracture of the matrix and fiber breakage near the matrix.

Influence of periodontal status and periodontopathogens on levels of oral human ß-defensin-2 in saliva.

BACKGROUND: Expression patterns of human ß-defensin-2 (HBD-2) mRNA or HBD-2 protein concentration and periodontal diseases have been a focus of scientific research. This study compares the salivary levels of HBD-2 protein concentration of healthy patients and patients with gingivitis and chronic periodontitis (CP) and correlates these levels with the presence of periodontopathogens. METHODS: A total of 89 patients were enrolled in this study: 31 periodontally healthy, 27 with gingivitis, and 31 with CP. Plaque and gingival indices, probing depth, and clinical attachment level were measured. The presence of Campylobacter rectus, Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, and Prevotella intermedia was evaluated qualitatively by conventional polymerase chain reaction. HBD-2 quantification in saliva was performed using an immune enzymatic assay. Frequency of periodontopathogens and HBD-2 protein concentration was assessed. Association between HBD-2 protein concentration (≥100 pg/mL) and the simultaneous presence of one to two, three to four, or five to six periodontopathogens was tested. RESULTS: Although periodontally healthy individuals and patients with gingivitis showed similar HBD-2 levels, the CP group displayed an increased level of HBD-2. P. gingivalis, P. intermedia, T. forsythia, and T. denticola were more prevalent in CP; however, their mere presence was not related to the increased levels of HBD-2 (Pearson correlation and multinomial logistic regression model). CONCLUSIONS: Salivary HBD-2 protein concentration was higher in patients with CP compared with healthy individuals or patients with gingivitis. These different protein concentrations were not related to the frequency of periodontopathogens. Clinical inflammatory profile had a higher impact on salivary HBD-2 levels than bacteria.

Reduction of salivary arginine catabolic activity through periodontal therapy.

OBJECTIVE: Salivary enzymes may be used to diagnose periodontal conditions. Salivary arginase activity (SAA) is related to susceptibility to bacterial infection. Therefore, the aim of this controlled interventional study was to determine the SAA before and after non-surgical periodontal therapy. METHOD AND MATERIALS: Eighty-nine subjects were selected: 31 periodontally healthy patients (controls), 27 gingivitis patients, and 31 chronic periodontitis patients. Plaque and Gingival Indices, probing depth, and clinical attachment level were monitored. The presence of Campylobacter rectus, Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, and Prevotella intermedia was evaluated by polymerase chain reaction. Salivary total protein level and SAA were also established by spectrophotometry. Clinical and arginase data were analyzed using the Wilcoxon, Mann-Withney, and Kruskal-Wallis tests (P < .05). For microbial data, the chi-square test was used. The Pearson correlation test was also used between each parameter evaluated. RESULTS: After therapy, due to a significant reduction in SAA, the values observed for the gingivitis and periodontitis groups were similar to those found in the healthy group. Interestingly, after therapy, SAA followed the same positive pattern showed by the overall improvement of clinical parameters (gingivitis and periodontitis groups mean values, pre- > posttherapy) and by the reduction of target pathogens (gingivitis group T forsythia, pre- > posttherapy; periodontitis group P. gingivalis, T. denticola, P. intermedia, and T. forsythia, pre- > posttherapy). CONCLUSION: Based on the reduction of SAA after therapy, in accordance with the expected reduction in clinical and microbiologic parameters, it was concluded that SAA has the potential to serve as a reliable method to access to the therapeutic response of chronic periodontitis subjects treated with nonsurgical periodontal therapy.

Spatial variation in the stable isotopes of 13C and 15N and trophic position of Leporinus friderici (Characiformes, Anostomidae) in Corumbá Reservoir, Brazil.

Stable isotopes of carbon (delta13C) and nitrogen (delta15N) were used to describe sources of energy and trophic position for adult Leporinus friderici in the area of the Corumbá Reservoir, Brazil. Samples were collected from April 1999 to March 2000. Spatial variations were not identified in the isotopic composition. The maximum and minimum contribution of C4 plants calculated integrating the variation of plants and fish were 47.7% and 2.4%, respectively. Among C3 plants, periphyton presented closer isotopic values to those observed for fishes, corresponding to an important carbon source. The proportion of ingested plant item is larger in rivers upstream from the reservoir (42.7%), which justifies the smaller trophic level among there. However, in the reservoir, the ingestion of fish was 81.4%, while ingested plants contributed with 18.6%. Downstream from the dam, participation of plant item was even smaller (14.4%). Although the trophic position calculated with diet data was proportional to the one calculated with delta15N values, the former elevated the trophic level of L. friderici in the food web, because estimated trophic positions were based on fish items belonging to the 2nd (a) and to the 3rd (b) trophic levels.

Spatial variation in the stable isotopes of 13C and 15N and trophic position of Leporinus friderici (Characiformes, Anostomidae) in Corumbá Reservoir, Brazil

Stable isotopes of carbon (delta13C) and nitrogen (delta15N) were used to describe sources of energy and trophic position for adult Leporinus friderici in the area of the Corumbá Reservoir, Brazil. Samples were collected from April 1999 to March 2000. Spatial variations were not identified in the isotopic composition. The maximum and minimum contribution of C4 plants calculated integrating the variation of plants and fish were 47.7 percent and 2.4 percent, respectively. Among C3 plants, periphyton presented closer isotopic values to those observed for fishes, corresponding to an important carbon source. The proportion of ingested plant item is larger in rivers upstream from the reservoir (42.7 percent), which justifies the smaller trophic level among there. However, in the reservoir, the ingestion of fish was 81.4 percent, while ingested plants contributed with 18.6 percent. Downstream from the dam, participation of plant item was even smaller (14.4 percent). Although the trophic position calculated with diet data was proportional to the one calculated with delta15N values, the former elevated the trophic level of L. friderici in the food web, because estimated trophic positions were based on fish items belonging to the 2nd (a) and to the 3rd (b) trophic levels.

Isótopos estáveis de carbono (delta13C) e nitrogênio (delta15N) foram utilizados para descrever as fontes de energia e a posição trófica de adultos de Leporinus friderici na área do reservatório de Corumbá, Brasil. As amostras foram coletadas entre abril de 1999 e março de 2000. Variações espaciais não foram identificadas quanto à composição isotópica da espécie. As contribuições máximas e mínimas das plantas C4, foram de 47,7 por cento e 2,4 por cento, respectivamente. Entre as plantas C3, o perífiton correspondeu a uma das mais importantes fontes de carbono para a espécie, pois seus valores isotópicos foram os mais próximos àqueles observados para os peixes. A proporção ingerida do item vegetal foi maior em rios localizados a montante do reservatório (42,7 por cento), justificando a menor posição trófica registrada para a espécie entre os ambientes estudados, enquanto no reservatório esta proporção foi de 18,6 por cento, sendo que o item peixes atingiu 81,4 por cento. A jusante do reservatório, a participação das plantas foi ainda menor, atingindo 14,4 por cento. Embora a posição trófica da espécie, calculada com os dados de dieta, fossem proporcionais àqueles calculados com os valores de delta15N, os primeiros elevaram o nível trófico de L. friderici na cadeia alimentar, pois estas foram baseadas nos itens peixe, cujas espécies pertenciam ao segundo e ao terceiro nível trófico.