A higher order model for thin-walled structures with deformable cross-sections

AbstractA higher order model for the analysis of linear, prismatic thin-walled structures that considers the cross-section warping together with the cross-section in-plane flexural deformation is presented in this paper. The use of a one-dimentional model for the analysis of thin-walled structures, which have an inherent complex three-dimensional (3D) behaviour, can only be successful and competitive when compared with shell finite element models if it fulfills a twofold objective: (i) an enrichment of the model in order to as accurately as possible reproduce its 3D elasticity equations and (ii) the definition of a consistent criterion for uncoupling the beam equations, allowing to identify structural deformation modes.The displacement field is approximated through a linear combination of products between a set of linear independent functions defined over the cross-section and the associated weights only dependent on the beam axis; this approximation is not constrained by any ab initio kinematic assumptions. Towards an efficient application of the approximation procedure, the cross-section is discretized into thin-walled elements, being the displacement field approximated for each element independently of the displacement direction. The approximation is thus hp refined enhancing the “capture” of the 3D structural mechanics of thin-walled structures. The beam model governing equations are obtained through the integration over the cross-section of the corresponding elasticity equations weighted by the cross-section global approximation functions.A criterion for uncoupling the beam governing equations is established, allowing to (i) retrieve the classic equations of the thin-walled beam theory both for open and closed sections and (ii) derive a set of uncoupled deformation modes representing higher order effects. The criterion is based on the solution of the polynomial eigenvalue problem associated with the beam differential equations, allowing to quantify the Saint-Venant principle for thin-walled structures. In fact, the solution of the non linear eigenvalue problem yields a twelve fold null eigenvalue (representing polynomial solutions) that are verified to represent beam classic solutions and sets of pairs and quadruplets of non-null eigenvalues corresponding to higher order modes of deformation

Effect Of Freezing Methods On The Properties Of Lyophilized Porous Silk Fibroin Membranes

Silk fibroin is a fibrous protein that has been extensively studied for application in the biomedical field, and has been used as a scaffold for bone tissue engineering. Biomaterials made of proteins are prone to physical and chemical degradation during storage; lyophilization, a drying method that consists of freezing and drying steps, is known to promote minimal changes in structure and biological activity of biomaterials. This study evaluates the effect of freezing methods on the properties of lyophilized porous silk fibroin membranes. The membranes were obtained from silk fibroin solution, frozen in liquid nitrogen or ultrafreezer, lyophilized, and then characterized by XRD, FTIR, TGA, DSC and SEM. Although the membranes presented similar physical, chemical and microstructural characteristics, quench freezing with liquid nitrogen, followed by lyophilization, promoted collapse of the membranes, while slow cooling performed by ultrafreezer preserved membrane integrity.122233237Tamada, Y., New process to form a silk fibroin porous 3-D structure (2005) Biomacromolecules, 6 (6), pp. 3100-3106Park, K., Jung, S., Lee, S., Min, B., Park, W., Biomimetic nanofibrous scaffolds: Preparation and characterization of chitin/silk fibroin blend nanofibers (2006) International Journal of Biological Macromolecules, 38 (3-5), pp. 165-173Sashina, E., Bochek, A., Novoselov, N., Kirichenko, D., Structure and solubility of natural silk fibroin (2006) Russian Journal of Applied Chemistry, 79 (6), pp. 869-876Vasconcelos, A., Freddi, G., Cavaco-Paulo, A., Biodegradable materials based on silk fibroin and keratin (2008) Biomacromolecules, 9 (4), pp. 1299-1305Roy, I., Gupta, M., Freeze-drying of proteins: Some emerging concerns (2004) Biotechnology and Applied Biochemistry, 39 (2), pp. 165-177Tang, X., Pikal, M., Design of freeze-drying processes for pharmaceuticals: Practical advice (2004) Pharmaceutical Research, 21 (2), pp. 191-200Sablani, S., Influence of shelf temperature on pore formation in garlic during freeze-drying (2006) Journal of Food Engineering, 80 (1), pp. 68-79Luthra, S., Obert, J., Kalonia, D., Pikal, M., Impact of critical process and formulation parameters affecting in-process stability of lactate dehydrogenase during the secondary drying stage of lyophilization: A mini freeze dryer study (2007) Journal of Pharmaceutical Sciences, 96 (9), pp. 2242-2250Wang, W., Lyophilization and development of solid protein pharmaceuticals (2000) International Journal of Pharmaceutics, 203 (1-2), pp. 1-60Rambhatla, S., Ramot, R., Bhugra, C., Pikal, M., Heat and mass transfer scale-up issues during freeze drying: II. control and characterization of the degree of supercooling (2004) AAPS PharmSciTech, 5 (4), pp. e58Chang, B., Kendrick, B., Carpenter, J., Surface-induced denaturation of proteins during freezing and its inhibition by surfactants (1996) Journal of Pharmaceutical Sciences, 85 (12), pp. 1325-1330Searles, J., Carpenter, J., Randolph, T., The ice nucleation temperature determines the primary drying rate of lyophilization for samples frozen on a temperature-controlled shelf (2001) Journal of Pharmaceutical Sciences, 90 (7), pp. 860-871Kim, H., Kim, U., Leisk, G., Bayan, C., Georgakoudi, I., Kaplan, D., Bone regeneration on macroporous aqueous-derived silk 3-D scaffolds (2007) Macromolecular Bioscience, 7 (5), pp. 643-655Wang, Y., Rudym, D., Walsh, A., Abrahamsen, L., Kim, H.J., Kim, H.S., In vivo degradation of three-dimensional silk fibroin scaffolds (2008) Biomaterials, 29 (24-25), pp. 3415-3428Ki, C., Park, S., Kim, H., Jung, H., Woo, K., Lee, J., Development of 3-D nanofibrous fibroin scaffold with high porosity by electrospinning: Implications for bone regeneration (2008) Biotechnology Letters, 30 (3), pp. 405-410Lv, Q., Feng, Q., Preparation of 3-D regenerated fibroin scaffolds with freeze drying method and freeze drying/foaming technique (2006) Journal of Materials Science: Materials in Medicine, 17 (12), pp. 1349-1356Beppu M, Polakiewicz B, Nogueira G. PI: 0601975-72006. INPI/Brazil2006Li, M., Lu, S., Wu, Z., Tan, K., Minoura, N., Kuga, S., Structure and properties of silk fibroin-poly(vinyl alcohol) gel (2002) International Journal of Biological Macromolecules, 30 (2), pp. 89-94Lin, F., Li, Y., Jin, J., Cai, Y., Wei, K., Yao, J., Deposition behavior and properties of silk fibroin scaffolds soaked in simulated body fluid (2008) Materials Chemistry and Physics, 111 (1), pp. 92-97Um, I., Kweon, H., Park, Y., Hudson, S., Structural characteristics and properties of the regenerated silk fibroin prepared from formic acid (2001) International Journal of Biological Macromolecules, 29 (2), pp. 91-97Zoccola, M., Aluigi, A., Vineis, C., Tonin, C., Ferrero, F., Piacentino, M.G., Study on cast membranes and electrospun nanofibers made from keratin/fibroin blends (2008) Biomacromolecules, 9 (10), pp. 2819-2825Kim, H.J., Kim, U., Kim, H.S., Li, C., Wada, M., Leisk, G., Bone tissue engineering with premineralized silk scaffolds (2008) Bone, 42 (6), pp. 1226-1234Bhatnagar, B., Bogner, R., Pikal, M., Protein stability during freezing: Separation of stresses and mechanisms of protein stabilization (2007) Pharmaceutical Development and Technology, 12 (5), pp. 505-52

Theoretical and experimental differential cross sections for electron impact excitation of the electronic bands of furfural

13 págs.; 8 figs.; 6 tabs.We report results from a joint experimental and theoretical investigation into electron scattering from the important industrial species furfural (CHO). Specifically, differential cross sections (DCSs) have been measured and calculated for the electron-impact excitation of the electronic states of CHO. The measurements were carried out at energies in the range 20-40 eV, and for scattered-electron angles between 10°and 90°. The energy resolution of those experiments was typically ∼80 meV. Corresponding Schwinger multichannel method with pseudo-potential calculations, for energies between 6-50 eV and with and without Born-closure, were also performed for a sub-set of the excited electronic-states that were accessed in the measurements. Those calculations were undertaken at the static exchange plus polarisation-level using a minimum orbital basis for single configuration interaction (MOB-SCI) approach. Agreement between the measured and calculated DCSs was qualitatively quite good, although to obtain quantitative accord, the theory would need to incorporate even more channels into the MOB-SCI. The role of multichannel coupling on the computed electronic-state DCSs is also explored in some detail. ©2016 AIP Publishing LLCR.F.C.N. thanks CNPq (Brazil) and the Science Without Borders Programme for opportunities to study abroad. D.B.J. thanks the Australian Research Council (ARC) for financial support provided through a Discovery Early Career Research Award, while M.J.B. also thanks the ARC for their support. M.J.B. and M.C.A.L. acknowledge the Brazilian agencies CNPq and FAPEMIG. P.L.-V. acknowledges the Portuguese Foundation for Science and Technology (FCTMEC) through Grant Nos. PTDC/FIS-ATO/1832/2012 and UIO/FIS/00068/2013. G.G. acknowledges partial financial support from the Spanish Ministry MINECO (Project No. FIS2012-31230) and the European Union COST Action No. CM1301 (CELINA). Finally, R.F.d.C., M.T.d.N.V., M.H.F.B., and M.A.P.L. acknowledge support from the Brazilian agency CNPq and M.T.d.N.V. also thanks FAPESP.Peer Reviewe

Avaliação da atividade fenilalanina amônia liásica em folhas de bananeira inoculadas com o fungo Mycosphaerella fijiensis.

O objetivo deste trabalho foi avaliar os atributos bioquímicos envolvidos na defesa da bananeira ao ataque do fungo M. fijiensis, notadamente avaliar o papel da enzima fenilalanina amônia liase nesta resposta, nas variedades Caprichosa, Garantida, FHIA-18, Prata Ken, Prata Anã, Maçã e Grande Naine, nos tempos: 0, 6h, 24h, 48h, 72h dias após a inoculação. Após a coleta, as folhas foram pesadas e obtidos os extratos totais por meio de maceração das folhas com tampão acetato de sódio 50 mM, pH 5,2, os quais foram utilizados nas determinações de proteínas e atividade enzimática