303 research outputs found
Axial-flexural coupled vibration and buckling of composite beams using sinusoidal shear deformation theory
A finite element model based on sinusoidal shear deformation theory is developed to study vibration and buckling analysis of composite beams with arbitrary lay-ups. This theory satisfies the zero traction boundary conditions on the top and bottom surfaces of beam without using shear correction factors. Besides, it has strong similarity with EulerâBernoulli beam theory in some aspects such as governing equations, boundary conditions, and stress resultant expressions. By using Hamiltonâs principle, governing equations of motion are derived. A displacement-based one-dimensional finite element model is developed to solve the problem. Numerical results for cross-ply and angle-ply composite beams are obtained as special cases and are compared with other solutions available in the literature. A variety of parametric studies are conducted to demonstrate the effect of fiber orientation and modulus ratio on the natural frequencies, critical buckling loads, and load-frequency curves as well as corresponding mode shapes of composite beams
Drought tolerance and antioxidant enzymatic activity in transgenic ?Swingle? citrumelo plants over-accumulating proline.
In this study we investigated the effects of the high endogenous proline level on water relations, gas exchange and antioxidant enzymatic activity in leaves of transgenic ?Swingle? citrumelo rootstocks transformed with the P5CSF129A gene coding for the key-enzyme for proline synthesis, under water deficit. Leaf total water, osmotic and pressure potentials, stomatal conductance, photosynthetic rates and xylem sapflowwere evaluated in non-transformed control and transgenic plants during water deficit treatment. Malondialdehyde (MDA) content, catalase (CAT; EC 1.11.1.6), superoxide dismutase (SOD; EC 1.15.1.1) and ascorbate peroxidase (APX; EC 1.11.1.11) activities were quantified in leaves collected based on their total water potential, representing the following conditions: irrigated (w =−1.3 MPa), moderate stress (w =−2.3 to −2.5 MPa), severe stress (w =−3.8 to −3.9 MPa) and recovery (24 h after re-irrigation: w =−1.3 to −1.9 MPa). Osmotic adjustment was observed in transgenic plants until 11 days after withholding water, while pressure potential in non-transformed controls was close to zero after nine days of water deprivation. This superior maintenance of turgor pressure in leaves of transgenic plants led to higher stomatal conductance, photosynthetic and transpiration rates when compared to non-transgenic plants. Drought caused a significant decrease in APX and SOD activities in control plants, followed by an increase after re-watering. On the other hand, CAT was more active in control than in transgenic plants under irrigated condition and both stress levels. Our results suggest that transgenic plants were able to cope with water deficit better than non-transformed controls since the high endogenous proline level acted not only by mediating osmotic adjustment, but also by contributing to gas exchange parameters and ameliorating deleterious effects of drought-induced oxidative stress
AnĂĄlise proteĂŽmica do estresse hĂdrico em cafeeiro.
DĂ©ficit hĂdrico Ă© um dos fatores ambientais mais importantes para a diminuição da produtividade do cafeeiro, tanto no Brasil quanto em outros paĂses produtores. O estabelecimento de estratĂ©gias para obtenção de cultivares tolerantes ao estresse hĂdrico depende da compreensĂŁo das respostas biolĂłgicas ao nĂvel genĂ©tico, molecular e bioquĂmico. Para estudar a resposta ao estresse hĂdrico no gĂȘnero Coffea, foi estabelecida uma rede de pesquisa em proteĂŽmica (PROTEOPAR ? Programa Proteoma do ParanĂĄ) constituĂda de oito laboratĂłrios. Quatro genĂłtipos de Coffea, com diferentes respostas fisiolĂłgicas Ă seca, foram analisados: C. canephora (Clone 14, tolerante e Clone 109A, sensĂvel) e C. arabica (BA10, tolerante e Geisha, sensĂvel). ProteĂnas foram extraĂdas de folhas e raĂzes de plantas (18 meses de idade) mantidas em casa-de-vegetação, utilizando-se o mĂ©todo de SDS-Fenol modificado. Os regimes hĂdricos constituĂram-se dos seguintes tratamentos: controle irrigado, estresse hĂdrico severo (-4,0 MPa de potencial de ĂĄgua) e recuperação pĂłs-estresse (36 horas apĂłs irrigação). Os extratos protĂ©icos foram distribuĂdos aos laboratĂłrios do PROTEOPAR para obtenção e anĂĄlise do padrĂŁo de expressĂŁo protĂ©ica diferencial via eletroforese bidimensional. O mĂ©todo de identificação de proteĂnas PMF (?Peptide mass fingerprinting?) foi aplicado utilizando-se um espectrĂŽmetro de massa (MS) do tipo MALDI-TOF e comparando os espectros de digestĂŁo trĂptica contra bancos de dados baseados em ESTs de Coffea
Assessment of Human Papillomavirus in Lung Tumor Tissue
Background Lung cancer kills more than 1 million people worldwide each year. Whereas several human papillomavirus (HPV)-associated cancers have been identified, the role of HPV in lung carcinogenesis remains controversial. Methods We selected 450 lung cancer patients from an Italian population-based case-control study, the Environment and Genetics in Lung Cancer Etiology. These patients were selected from those with an adequate number of unstained tissue sections and included all those who had never smoked and a random sample of the remaining patients. We used real-time polymerase chain reaction (PCR) to test specimens from these patients for HPV DNA, specifically for E6 gene sequences from HPV16 and E7 gene sequences from HPV18. We also tested a subset of 92 specimens from all never-smokers and a random selection of smokers for additional HPV types by a PCR-based test for at least 54 mucosal HPV genotypes. DNA was extracted from ethanol- or formalin-fixed paraffin-embedded tumor tissue under strict PCR clean conditions. The prevalence of HPV in tumor tissue was investigated. Results Specimens from 399 of 450 patients had adequate DNA for analysis. Most patients were current (220 patients or 48.9%) smokers, and 92 patients (20.4%) were women. When HPV16 and HPV18 type-specific primers were used, two specimens were positive for HPV16 at low copy number but were negative on additional type-specific HPV16 testing. Neither these specimens nor the others examined for a broad range of HPV types were positive for any HPV type. Conclusions When DNA contamination was avoided and state-of-the-art highly sensitive HPV DNA detection assays were used, we found no evidence that HPV was associated with lung cancer in a representative Western population. Our results provide the strongest evidence to date to rule out a role for HPV in lung carcinogenesis in Western populations
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