187 research outputs found
Nota a la Farmacopea Española IX edición: Antipirina
Se estudia la monografía «Antipyrina» de la F. E. IX comparativamente con el existente en las demás farmacopeas y se proponen diversas modificaciones a la misma basadas en datos experimentales.The monograph "Antipyrine" spanish pharmacopoeia IX is studied comparatively with that in other pharmacopoeia and various modifications to it based on experimental data is proposed.Cátedra de Farmacia Galénica y Técnica Profesional y Legislación (Prof. Dr. José M. Suñé Arbussá
Microestructura del esmalte de los incisivos de roedores (Mammalia, Rodentia)
Abstract not availabl
Computational micromechanics of fiber kinking in unidirectional FRP under different environmental conditions
The determination of ply properties of Fiber Reinforced Polymers (FRP) for particular operational environmental conditions in aeronautical applications is mandatory in order to fulfill current industry stringent certification requirements. However, the traditional experimental approach requires massive investments of resources and time. From the behaviour obtained experimentally, constitutive equations including failure criteria are then devised to be used in the design of FRP structures. The ply longitudinal behaviour under compression is generally the most difficult to measure and characterize. In this work, an alternative coupled experimental-computational micromechanics approach is proposed to determine the longitudinal compression properties of unidirectional FRP plies under different environmental conditions. This methodology includes experimental characterization of matrix and fiber/matrix interface, combined with numerical simulations of realistic microstructures. The interface decohesion is simulated using cohesive-frictional interactions. A pressure dependent, elasto-plastic model that includes tensile damage is employed to capture the matrix nonlinear behaviour. The numerical predictions match the experimentally-obtained ply properties available in the literature in a remarkable way and suggest that virtual ply property characterization is a mature and reliable approach to conduct screening of materials.The authors would like to acknowledge the support provided by AIRBUS SAS through the project SIMSCREEN (Simulation for Screening Composite Materials Properties). Additionally, C.S. Lopes acknowledges the support of the Spanish Ministry of Economy and Competitiveness (RYC-2013-14271) through the Ramón y Cajal program. The collaboration with NASA Langley Research Center in some aspects of this work is also acknowledged
Special-purpose elements to impose Periodic Boundary Conditions for multiscale computational homogenization of composite materials with the explicit Finite Element Method
A novel methodology is presented to introduce Periodic Boundary Conditions (PBC) on periodic Representative Volume Elements (RVE) in Finite Element (FE) solvers based on dynamic explicit time integration. This implementation aims at overcoming the difficulties of the explicit FE method in dealing with standard PBC. The proposed approach is based on the implementation of a user-defined element, named a Periodic Boundary Condition Element (PBCE), that enforces the periodicity between periodic nodes through a spring-mass-dashpot system. The methodology is demonstrated in the multiscale simulation of composite materials. Two showcases are presented: one at the scale of computational micromechanics, and another one at the level of computational mesomechanics. The first case demonstrates that the proposed PBCE allows the homogenization of composite ply properties through the explicit FE method with increased efficiency and similar reliability with respect to the equivalent implicit simulations with traditional PBC. The second case demonstrates that the PBCE coupled with Periodic Laminate Elements (PLE) can effectively be applied to the computational homogenization of elastic and strength properties of entire laminates taking into account highly nonlinear effects. Both cases motivate the application of the methodology in multiscale virtual testing in support of the building-block certification of composite materials.The research leading to this publication was supported by the European Community FP7 Programme through project MAAXIMUS (grant agreement 213371) and by the Spanish Ministry of Industry, Economy and Competitiveness (MINECO) through project HYDTCOMP (grant MAT2015-69491-C03-02). C.S. Lopes also acknowledges the support of MINECO through the Ramón y Cajal fellowship (grant RYC-2013-14271). The authors are grateful to Prof. Ignacio Romero for his helpful insights on this research
Multiscale modelling of thermoplastic woven fabric composites: From micromechanics to mesomechanics
The mechanical properties of woven composites can be predicted by using a multiscale modelling approach. The starting point to its application is the microscale (the level of fibres, matrix and interfaces), that allows the computation of the homogenised behaviour of the yarn. The aim of this work was to predict the yarn-level behaviour of a thermoplastic-based woven composite in order to allow the formulation of a representative constitutive model that can be used to predict ply properties at the mesoscale. To accomplish this purpose, an in situ characterisation of the microconstituents was carried out. This served to generate inputs for three different representative volume element (RVE) models that allowed predicting the yarn longitudinal, transverse and shear responses. These mechanical characteristics allowed the determination of homogenised yarn constitutive behaviour which was found to be characterised by significant non-linearity until failure, specially in transverse and shear directions.The research leading to the developments described received funding of the project ADVANSEAT; a collaborative R&D project led by Grupo Antolín, and partially supported by the Spanish Ministry of Economy, Industry and Competitiveness (MINECO). C.S. Lopes also acknowledges the support of MINECO through the Ramón y Cajal fellowship (RYC-2013-14271)
All-fiber tunable optical delay line
We present a tunable optical delay line based on the use of a
single chirped fiber Bragg grating written into a standard single mode
optical fiber. In the proposed scheme, the delay is induced through the
Bragg grating differential group delay curve. This is achieved by launching
orthogonally polarized optical pulses in both directions into the Bragg
grating and by controlling its local birefringence. This bidirectional
propagation allows to compensate the second-order dispersion. The setup is
suitable to delay pulses with a spectral width just less than the grating
reflection bandwidth, which is particularly useful in the context of
forthcoming wavelength division multiplexing ultra-high bit rate lightwave
systems. In this work, the performances of the setup are investigated using a
pulsed laser delivering 6.3 ps Fourier transform limited pulses at 1548 nm.
A maximum delay of 120 ps (about 20 times the pulse width) is reported
experimentally
Two isoforms of vasa maternal factor in Senegalese sole: Biotechnological applications
Primordial Germ Cells (PGCs)
identification and manipulation
present considerable potential
for hatchery practice and
surrogate broodstocks.
To carry out the PGCs
characterization a specific
molecular marker is required.
The vasa gene is a good
candidate to identify PGCs and
others germinal cells (Nagasawa
et al., 2009).
The aim of this study was the
cloning of the Solea senegalensis
vasa cDNA and its expression
pattern during early development
and adulthood
Processing and mechanical properties of novel biodegradable poly-lactic acid/Zn 3D printed scaffolds for application in tissue regeneration
The feasibility to manufacture scaffolds of poly-lactic acid reinforced with
Zn particles by fused filament fabrication is demonstrated for the first time.
Filaments of 2.85 mm in diameter of PLA reinforced with different weight
fractions of m-sized Zn - 1 wt. \% Mg alloy particles (in the range 3.5 to
17.5 wt. \%) were manufactured by a double extrusion in method in which
standard extrusion is followed by a precision extrusion in a filament-maker
machine. Filaments with constant diameter, negligible porosity and a
homogeneous reinforcement distribution were obtained for Zn weight fractions of
up to 10.5\%. It was found that the presence of Zn particles led to limited
changes in the physico-chemical properties of the PLA that did not affect the
window temperature for 3D printing nor the melt flow index. Thus, porous
scaffolds could be manufactured by fused filament fabrication at 190\textdegree
C with poly-lactic acid/Zn composites containing 3.5 and 7 wt. \% of Zn and at
170\textdegree C when the Zn content was 10.5 wt. \% with excellent dimensional
accuracy and mechanical properties
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