Finite element models of biomedical applications increasingly use anisotropic hyperelastic material formulations. Appropriate material parameters are essential for a reliable outcome of these ...simulations, which is why planar biaxial testing of soft biological tissues is gaining importance. However, much is still to be learned regarding the ideal methodology for performing this type of test and the subsequent parameter fitting procedure. This paper focuses on the effect of an unknown sample orientation or a mistake in the sample orientation in a planar biaxial test using rakes. To this end, finite element simulations were conducted with various degrees of misalignment. Variations to the test method and subsequent fitting procedures are compared and evaluated. For a perfectly aligned sample and for a slightly misaligned sample, the parameters of the Gasser-Ogden-Holzapfel model can be found to a reasonable accuracy using a planar biaxial test with rakes and a parameter fitting procedure that takes into account the boundary conditions. However, after a certain threshold of misalignment, reliable parameters can no longer be found. The level of this threshold seems to be material dependent. For a sample with unknown sample orientation, material parameters could theoretically be obtained by increasing the degrees of freedom along which test data is obtained, e.g. by adding the data of a rail shear test. However, in the situation and the material model studied here, the inhomogeneous boundary conditions of the test set-ups render it impossible to obtain the correct parameters, even when using the parameter fitting method that takes into account boundary conditions. To conclude, it is always important to carefully track the sample orientation during harvesting and preparation and to minimize the misalignment during mounting. For transversely isotropic samples with an unknown orientation, we advise against parameter fitting based on a planar biaxial test, even when combined with a rail shear test.
In this study, a novel time-domain multiple reflection method for determining the electrical properties and thickness of the sample has been proposed. The unique advantage of this method is that it ...employs only reflection coefficient data for the reconstruction of the properties. The proposed scheme is validated by determining the permittivity, thickness, and loss tangent values of different samples of different thicknesses with high accuracy. The experimental characterisation has been carried out, incorporating the proposed scheme for its verification and thereby the electrical and physical properties of an unknown sample have been retrieved. The proposed method is simple, cost-effective and non-iterative in nature. The proposed technique is quite useful in applications like through-wall imaging, where the wall can be accessed from a single side only, monitoring the health of the building and ground-penetrating radar.
The connection between chocolate and cocoa is studied. As cocoa is produced in different countries, samples coming from the same geographical region are analysed. The analyses focus on the ...characterisation of the considered samples for different aspects of quality and to individuate the original locations of production, also connecting this with the nutritional aspects. For this purpose, qualitative and quantitative traditional analysis and determination of fatty acid content are performed. The obtained experimental data show interesting correlations. The percentages of fatty acids computed allow for distinctions to be made among cocoa and chocolate samples. Furthermore, a relation can be assumed among the data obtained for primary matters and final products corresponding to countries being positioned on the same latitude, even if they are situated in different continents.
This paper demonstrates that rejecting the standard definition of full-time and part-time workers, the estimated number of hours that an individual is likely to work as a full-time worker is a ...function of the type of distribution one assumes about the error term in the wage equation. Adopting a switching regression model with unknown sample selection, we have found that the normality assumption generates higher hours for full-timers in comparison with the non-normal distributions. We also noted that regardless of the distribution assumed, the hours differ from one industry to another. The implication is that the standard definition of full-time and part-time worker may not be appropriate for all firms irrespective of the distribution assumed. The paper also shows the sensitivity of parameter estimates to the distributional assumptions about the error term in the wage equation. The results indicate that the normal distribution wage equation estimates are relatively larger than the Weibull and exponential distributions. This finding is particularly important because such differences in estimated coefficients may have a direct wage influence on the wage gap between full-time and part-time workers across distributions.
Identification of an unknown substance without any information remains a daunting challenge despite advances in chemistry and mass spectrometry. However, an unknown cyclic peptide in a sample with ...very limited volume seized at a Pennsylvania racetrack has been successfully identified. The unknown sample was determined by accurate mass measurements to contain a small unknown peptide as the major component. Collision-induced dissociation (CID) of the unknown peptide revealed the presence of Lys (not Gln, by accurate mass), Phe, and Arg residues, and absence of any y-type product ion. The latter, together with the tryptic digestion results of the unusual deamidation and absence of any tryptic cleavage, suggests a cyclic structure for the peptide. Electron-transfer dissociation (ETD) of the unknown peptide indicated the presence of Gln (not Lys, by the unusual deamidation), Phe, and Arg residues and their connectivity. After all the results were pieced together, a cyclic tetrapeptide, cycloArg-Lys-N(C
6
H
9
)Gln-Phe, is proposed for the unknown peptide. Observations of different amino acid residues from CID and ETD experiments for the peptide were interpreted by a fragmentation pathway proposed, as was preferential CID loss of a Lys residue from the peptide. ETD was used for the first time in sequencing of a cyclic peptide; product ions resulting from ETD of the peptide identified were categorized into two types and named pseudo-b and pseudo-z ions that are important for sequencing of cyclic peptides. The ETD product ions were interpreted by fragmentation pathways proposed. Additionally, multi-stage CID mass spectrometry cannot provide complete sequence information for cyclic peptides containing adjacent Arg and Lys residues. The identified cyclic peptide has not been documented in the literature, its pharmacological effects are unknown, but it might be a “designer” drug with athletic performance-enhancing effects.
In the traditional framework of multivariate spectroscopic calibration, the most popular method, partial least squares (PLS), shrinks the regression coefficients based on the information of training ...sample concentrations. Motivated by the concept of parallel calibration, the second direction for shrinkage of regression coefficients, the direction towards unknown sample spectra is investigated in this paper. A different multivariate calibration method, parallel calibration model based on partial least squares, PCPLS is proposed. With both theoretical support and analysis of some real data sets, it is demonstrated that the second shrinkage direction is at least as natural and necessary as the traditional one. An interesting difference of the proposed method from traditional methods is the involvement of unknown sample spectra and consideration of their error in the training process. Some new related problems and potential applications of this method are also briefly discussed.
In this paper bulk sample prompt gamma neutron activation analysis (BSPGNAA) was applied to aqueous sample analysis using a relative method. For elemental analysis of an unknown bulk sample, gamma ...self-shielding coefficient was required. Gamma self-shielding coefficient of unknown samples was estimated by an experimental method and also by MCNP code calculation. The proposed methodology can be used for the determination of the elemental concentration of unknown aqueous samples by BSPGNAA where knowledge of the gamma self-shielding within the sample volume is required.
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