Microstructure-based modeling of elastic functionally graded materials: One dimensional case

Functionally graded materials (FGMs) are two-phase composites with continuously changing microstructure adapted to performance requirements. Traditionally, the overall behavior of FGMs has been determined using local averaging techniques or a given smooth variation of material properties. Although these models are computationally efficient, their validity and accuracy remain questionable, since a link with the underlying microstructure (including its randomness) is not clear. In this paper, we propose a modeling strategy for the linear elastic analysis of FGMs systematically based on a realistic microstructural model. The overall response of FGMs is addressed in the framework of stochastic Hashin-Shtrikman variational principles. To allow for the analysis of finite bodies, recently introduced discretization schemes based on the Finite Element Method and the Boundary Element Method are employed to obtain statistics of local fields. Representative numerical examples are presented to compare the performance and accuracy of both schemes. To gain insight into similarities and differences between these methods and to minimize technicalities, the analysis is performed in the one-dimensional setting.Comment: 33 pages, 14 figure

Bioactive Phenolics from Carthamus lanatus L.

Two flavonoid aglycons, eight flavonoid glycosides, chlorogenic acid and syringin were isolated from aerial parts of Carthamus lanatus. Isorhamnetin 3-O-β-D-glucoside and chlorogenic acid were found for the first time in the genus Carthamus and respectively, quercimeritrin, astragalin, kaempferol 3-O-β-D-sophoroside and syringin in the species. The ethyl acetate fraction of the methanol extract exhibited a higher antioxidant activity than the butanol fraction measured by the α,α-diphenyl-β -picrazylhydrazyl (DPPH) free radical scavenging assay. Cytotoxicity and antioxidant activities of the main constituent, luteolin 7-O-β-D-glucoside, were evaluated

Oxygenated bisabolane fucosides from Carthamus lanatus L.

The aerial parts of Carthamus lanatus (Asteraceae) afforded four new oxygenated bisabolane fucosides, 10-hydroperoxy-bisabola-2,11-diene 7-O-β-D-fucopyranoside, 11-hydroperoxy-bisabola-2,9-diene 7-O-β-D-fucopyranoside, 10-hydroxy-bisabola-2,11-diene 7-O-β-D- fucopyranoside and 11-hydroxy-bisabola-2,9-diene 7-O-β-D-fucopyranoside together with the known compounds α-bisabolol β-D-fucopyranoside, asperuloside, sitosterol 3-O-β-D-glucoside and stigmasterol 3-O-β-D-glucoside. Asperuloside appears to be the second representative of the iridoid monoterpene group found in the plant family Asteraceae, which until recently was considered to lack iridoids. The main constituent α-bisabolol fucoside exhibited noticeable antibacterial and cytotoxic activities

Clastogenic Effect of Carthamus lanatus L. (Asteraceae)

The clastogenic effect of total dichloromethane, methanol and water extracts, four bioactive fractions and three individual constituents from Carthamus lanatus aerial parts were evaluated in mice by bone marrow chromosome aberration assay with mitomycin C as positive control. Significant differences in the percentage of aberrant mitosis of the extracts were observed. The dichloromethane extract exhibited a considerable clastogenic effect and the water extract a negligible one. Different types of chromosome aberrations and time-dependant effects for the active fractions and individual compounds were found

NMR Investigation and Conformational Analysis of a Synthetic Hexasaccharide

The structure of the hexasaccharide 1 has been examined by a spectroscopic investigation using one- and two-dimensional NMR spectroscopy. All 1H and 13C signals of the saccharide part were assigned. NOESY and ROESY experiments allowed to discuss the flexibility of the molecule

In vitro Anti-inflammatory Effect of Carthamus lanatus L.

The anti-inflammatory activity of four total extracts, their fractions and two main constituents (α-bisabolol β-D-fucopyranoside and luteolin 7-O-glucoside) of Carthamus lanatus L. aerial parts, were assessed in vitro by determining the inhibitory effects on induced human neutrophils. The dichloromethane extract and its water-alcoholic part exhibited the most significant inhibitory effects

A Novel Triterpene Saponin from Gypsophila capillaris

A novel C-28 tetraglycoside of quillaic acid (1) has been isolated from Gypsophila capillaris. The structure was elucidated by 1 D NMR (NOE difference, DEPT, selective13C{1H} INEPT), 2D NMR (1H,1H and1H,13C COSY,1H,1H,1H RELAY, ROESY and TOCSY) and other spectroscopic and chromatographic evidences. Conformational dynamics within the tetrasaccharide part were estimated from NOE responses and ROESY peaks. © 1995 Verlag der Zeitschrift für Naturforschung. All rights reserved

SQG-Differential Evolution for difficult optimization problems under a tight function evaluation budget

In the context of industrial engineering, it is important to integrate efficient computational optimization methods in the product development process. Some of the most challenging simulation-based engineering design optimization problems are characterized by: a large number of design variables, the absence of analytical gradients, highly non-linear objectives and a limited function evaluation budget. Although a huge variety of different optimization algorithms is available, the development and selection of efficient algorithms for problems with these industrial relevant characteristics, remains a challenge. In this communication, a hybrid variant of Differential Evolution (DE) is introduced which combines aspects of Stochastic Quasi-Gradient (SQG) methods within the framework of DE, in order to improve optimization efficiency on problems with the previously mentioned characteristics. The performance of the resulting derivative-free algorithm is compared with other state-of-the-art DE variants on 25 commonly used benchmark functions, under tight function evaluation budget constraints of 1000 evaluations. The experimental results indicate that the new algorithm performs excellent on the 'difficult' (high dimensional, multi-modal, inseparable) test functions. The operations used in the proposed mutation scheme, are computationally inexpensive, and can be easily implemented in existing differential evolution variants or other population-based optimization algorithms by a few lines of program code as an non-invasive optional setting. Besides the applicability of the presented algorithm by itself, the described concepts can serve as a useful and interesting addition to the algorithmic operators in the frameworks of heuristics and evolutionary optimization and computing

Experimental characterisation of porcine subcutaneous adipose tissue under blunt impact up to irreversible deformation

A deeper understanding of the mechanical characteristics of adipose tissue under large deformation is important for the analysis of blunt force trauma, as adipose tissue alters the stresses and strains that are transferred to subjacent tissues. Hence, results from drop tower tests of subcutaneous adipose tissue are presented (i) to characterise adipose tissue behaviour up to irreversible deformation, (ii) to relate this to the microstructural configuration, (iii) to quantify this deformation and (iv) to provide an analytical basis for computational modelling of adipose tissue under blunt impact. The drop tower experiments are performed exemplarily on porcine subcutaneous adipose tissue specimens for three different impact velocities and two impactor geometries. An approach based on photogrammetry is used to derive 3D representations of the deformation patterns directly after the impact. Median values for maximum impactor acceleration for tests with a flat cylindrical impactor geometry at impact velocities of 886~mm/s, 1253~mm/s and 2426~mm/s amount to 61.1~g, 121.6~g and 264.2~g, respectively, whereas thickness reduction of the specimens after impact amount to 16.7%, 30.5% and 39.3%, respectively. The according values for tests with a spherically shaped impactor at an impact velocity of 1253~mm/s are 184.2~g and 78.7%. Based on these results, it is hypothesised that, in the initial phase of a blunt impact, adipose tissue behaviour is mainly governed by the behaviour of the lipid inside the adipocytes, whereas for further loading, contribution of the extracellular collagen fibre network becomes more dominant