The differentiation status of primary gonadal germ cell tumors correlates inversely with telomerase activity and the expression level of the gene encoding the catalytic subunit of telomerase

BACKGROUND: The activity of the ribonucleoprotein enzyme telomerase is detectable in germ, stem and tumor cells. One major component of telomerase is human telomerase reverse transcriptase (hTERT), which encodes the catalytic subunit of telomerase. Here we investigate the correlation of telomerase activity and hTERT gene expression and the differentiation status of primary testicular germ cell tumors (TGCT). METHODS: Telomerase activity (TA) was detected by a quantitative telomerase PCR ELISA, and hTERT mRNA expression was quantified by online RT-PCR in 42 primary testicular germ cell tumors. The control group consisted of benign testicular biopsies from infertile patients. RESULTS: High levels of telomerase activity and hTERT expression were detected in all examined undifferentiated TGCTs and in the benign testicular tissue specimens with germ cell content. In contrast, differentiated teratomas and testicular control tissue without germ cells (Sertoli-cell-only syndrome) showed no telomerase activity and only minimal hTERT expression. CONCLUSIONS: These findings demonstrate an inverse relationship between the level of telomerase activity and hTERT mRNA expression and the differentiation state of germ cell tumors. Quantification of telomerase activity and hTERT mRNA expression enables a new molecular-diagnostic subclassification of germ cell tumors that describes their proliferation potential and differentiation status

Beitrag zur deformationsmechanischen Charakterisierung mehrschichtiger Schalen

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Interface fracture of polymer films : blister test experiments and modelling

The interface fracture between a rigid substrate and polymer film is investigated in this work using pressurised blister test experiments and modelling. The interface crack growth is studied for two different types of polymer films: stiff and compliant ones. The pressurised blister test is used to provide critical pressure-crack length curves for different loading media (water and electrolyte solutions) and loading rates. Two different analytical approaches and a numerical modelling concept are used to determine the critical total energy release rate as a function of the crack length (crack resistance curve or R-curve). A relatively flat R-curve is observed for the system with the stiff polymer film, whilst R-curve for the compliant film system exhibits an increasing tendency. The mixed-mode fracture behaviour occurs for both investigated polymer film systems, as shown by the value of the mixed-mode angle that is constant for all investigated crack lengths. R-curves are nearly unaffected by different loading media, whereas the loading rate has a strong influence on the interface fracture of the compliant file system. Finite element method-based prediction of the total energy release rate is in good agreement with that obtained from analytical expressions

Analysis of a compression shear fracture test for curved interfaces in layered composites

The goal of this paper is computational analysis of a compression shear fracture test, proposed for interface fracture toughness determination and crack propagation analysis in curved layered composites. The main difficulty of the test is that crack surfaces come into contact. Thus, friction is an energy absorbing mechanism, that superimposes with other irreversible phenomena––an energy released during crack extension. Numerical analysis using contact finite elements is paid to the near crack-tip displacements and stresses. The comparison between finite element method and analytically determined stresses is made. This study shows that energy release rate of the composite considered strongly depends on the interfacial friction coefficient

Notched-butt test for the determination of adhesion strength at bimaterial interfaces

For the experimental determination of adhesion strength between materials it is desirable to have a uniform stress distribution within the interface of the specimen. The common butt-test with a flat interface between two adhering materials produces stress singularities at the edges of the specimen but shows uniform stress distribution along the interface within the material. To avoid a premature failure at the edge due to the presence of the singular stress field, a notch can be machined at the interface within one of the materials. For isotropic materials, the notch geometry depends on the Dundurs parameters of the bimaterial system. This notch produces a certain local material angle and eliminates stress singularities at the specimen edges. Analytical and finite-element calculations provide the notch geometry appropriate for uniform stress distribution along the whole interface. The applicability of the test is proven by the determination of adhesion strength between polycarbonate and thermoplastic polyurethane. © 2012 Koninklijke Brill NV, Leiden

Tensile and shear strength of bimaterial interfaces within composite materials

The determination of the tensile and shear strengths of homogeneous materials can be easily performed by standard tensile and shear (e.g. Iosipescu) tests. Nevertheless, when the determination of these strengths involves a bimaterial interface, the standard samples present bimaterial corner configurations at their free-edges which generate singular stress fields. In the presence of these singular stress fields, the tensile and shear stress distributions are strongly non-uniform at these edges, where failure initiates and propagates along the bimaterial interface. The apparent strength obtained from these tests is not representative of the regularized strength of the bimaterial interface. To eliminate the stress singularities, a small notch is made on one of the materials along the interface perimeter, in this study. This idea, originally proposed by Lauke and Barroso (Compos. Interface, 18:661-669, 2011) for ascertaining tensile strength, is now adapted to ascertain shear strength, using a modified geometry of the Iosipescu sample, and it has also been generalized to configurations involving composite materials. Both proposals, for the tensile and shear tests, are performed using the bimaterial configuration of a composite and an adhesive; a bimaterial interface which typically appears in adhesive joints with composites. The local notch geometry is defined using semi-analytical tools developed by the authors and numerically verified by Finite Element models. The modified bimaterial geometries, tested under tension, demonstrated a higher tensile strength. However, the modified bimaterial geometries tested in shear did not show any clear influence over the failure load with or without the notch in the particular bimaterial configuration tested in this study. © 2016 Elsevier Ltd

A novel fiber treatment applied to woven jute fabric/vinylester laminates

In this work, a novel fiber treatment consisting on an alkali treatment superimposed to biaxial tensile stress was successfully applied to woven jute fabric/vinylester laminates. The effect of treatment on the composites tensile properties was investigated at two different times of treatment. A significant improvement in stiffness was achieved by the composite treated with alkali under stress for 4 h. However, no significant differences between the stiffness of the untreated composite and the composites treated with alkali under stress for 24 h were found. On the other hand, irrespectively of the time of treatment, the composites with fabrics treated with alkali under stress showed the highest values of tensile strength. From results of fabrics tensile tests, compression shear tests and X-ray diffraction analysis, the improved tensile properties exhibited by the composites with treated fabrics could be attributed to structural changes of the fibers as well as to a change in the fiber/matrix interfacial properties.Fil: Stocchi, Ariel Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Lauke, Bernd. Leibniz Institute of Polymer Research; AlemaniaFil: Vázquez, Analía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Bernal, Celina Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin