Fracture mechanisms in biopolymer films using coupling of mechanical analysis and high speed visualization technique

The aim of this study was to provide a detailed description of the fracture mechanisms in three different biopolymer thin materials: gelatin, hydroxypropyl cellulose (HPC) and cassava starch films. That was achieved by using a combination of fracture mechanics methodology and in situ visualization with high speed imaging technique. By analyzing the unstable and stable crack propagation that occurs in these materials, the brittle to ductile transition induced by water plasticization was assessed and discussed. Each biopolymer material exhibited a distinctive brittle and ductile fracture mode, which were described in this work. In order to evaluate the occurrence of permanent deformation in the proximity of the crack propagation front, FTIR maps with polarized light microscopy were employed, which enabled the visualization of structural homogeneity and cohesivity. The differences in fracture behaviour were interpreted taking into account the structural organization within these materials during stretching. The coupling of mechanical data and advanced visualization techniques was a particularly effective method to describe and interpret the complex fracture mechanisms in biopolymer materials which is strongly affected by their interaction with water molecules. © 2010 Elsevier Ltd. All rights reserved

Biomphalaria tenagophila : genetic variability within intermediate snail hosts susceptible and resistant to Schistosoma mansoni infection

DNA analysis by molecular techniques has significantly expanded the perspectives of the study and understanding of genetic variability in molluscs that are vectors of schistosomiasis. In the present study, the genetic variability of susceptible and resistant B. tenagophila strains to S. mansoni infection was investigated using amplification of their genomic DNA by RAPD-PCR. The products were analyzed by PAGE and stained with silver. The results showed polymorphism between tested strains with four different primers. We found two bands of 1,900 and 3,420 bp that were characteristic of the susceptible strains with primer 2. The primers 9 and 10 identified a single polymorphic band that was also characteristic of (3, 136 and 5,041 bp, respectively) susceptible snails. Two polymorphic bands were detected by primer 15 : one with 1,800 bp was characteristic of the resistant strain and the other with = 1,700 bp in the susceptible one. These results provide additional evidence showing that the RAPD-PCR technique is adequate for the study of polymorphisms in intermediate hosts snails of S. mansoni. The obtained results are expected to expand the knowledge about the genetic variability of the snails and to permit the future identification of genomic sequences specifically related to the resistance/susceptibility of Biomphalaria to the larval forms of S. mansoni

: genetic variability within intermediate snail hosts susceptible and resistant to

DNA analysis by molecular techniques has significantly expanded the perspectives of the study and understanding of genetic variability in molluscs that are vectors of schistosomiasis. In the present study, the genetic variability of susceptible and resistant B. tenagophila strains to S. mansoni infection was investigated using amplification of their genomic DNA by RAPD-PCR. The products were analyzed by PAGE and stained with silver. The results showed polymorphism between tested strains with four different primers. We found two bands of 1,900 and 3,420 bp that were characteristic of the susceptible strains with primer 2. The primers 9 and 10 identified a single polymorphic band that was also characteristic of (3, 136 and 5,041 bp, respectively) susceptible snails. Two polymorphic bands were detected by primer 15 : one with 1,800 bp was characteristic of the resistant strain and the other with = 1,700 bp in the susceptible one. These results provide additional evidence showing that the RAPD-PCR technique is adequate for the study of polymorphisms in intermediate hosts snails of S. mansoni. The obtained results are expected to expand the knowledge about the genetic variability of the snails and to permit the future identification of genomic sequences specifically related to the resistance/susceptibility of Biomphalaria to the larval forms of S. mansoni

Correlation between sperm characteristics and testosterone in bovine seminal plasma by direct radioimmunoassay

The objectives of this study were to validate a non-extractive RIA for seminal testosterone and quantify the hormone using a solid-phase commercial kit, and study the correlation between testosterone in seminal plasma and sperm characteristics. Parallelism showed a correlation index r = 0.992 (Y = -5.47 + 1.073X; R² = 0.985), indicating that the non-extractive method presented is indicated particularly for assessment of testosterone when establishing comparisons between samples. Overall mean (±SD) of testosterone level was 0.60±0.65 ng/mL. Correlation was only found between the seminal concentrations of testosterone and pH of the semen

Mechanical properties and total hydroxycinnamic derivative release of starch/glycerol/Melissa officinalis extract films

The aim of this study was to investigate the mechanical properties of starch/glycerol/Melissa officinalis, a topical drug delivery system for labial herpes treatment. Four films were prepared with different concentrations of starch, glycerol, and Melissa officinalis extract. The results revealed that increasing the glycerol concentration in the film reduced elasticity modulus and tensile strength, exhibiting a plasticizing effect. The increase in free volume resulted in increased release of hydroxycinnamic derivatives expressed as rosmarinic acid.<br>O objetivo deste trabalho foi estudar as propriedades mecânicas e o mecanismo de liberação de um sistema tópico de liberação prolongada para o tratamento do Herpes labial a partir de filmes de amido/glicerol/extrato de Melissa officinalis, planta com comprovada atividade antiviral. Foram obtidos quatro filmes poliméricos com diferentes concentrações de amido, glicerol e extrato de Melissa officinalis os quais foram caracterizados mecanicamente e determinado o perfil de liberação de derivados hidroxicinâmicos. Os resultados demonstraram que o aumento da concentração de glicerol no filme produz uma redução no módulo de elasticidade e na tensão de deformação como conseqüência do efeito plastificante. O aumento no volume livre do polímero resultou em aumento da liberação dos derivados hidroxicinâmicos expressos como ácido rosmarínico