Machining of reproducible flaws corresponding to fatigue cracks for fracture mechanics tests of components and welded joints

In connection with the analysis and the development of failure concepts in fracture mechanics for quasistatic loaded components and elastic-plastic behaviour of the material, tests are also carried out with welded and/or complex shaped specimens or structures. Thereby the difficulty arises of generating reproducible flaws in the form of fatigue precracks in definite positions in the components, respectively in the welded joint. It is reported exemplarily about experiments on different CT25 and CCT specimens and on a pressure vessel which contained a fatigue pre-crack, a 0.2 mm saw cut or notches with notch root radius ≤ ≥ 0.1 mm as flaws. The comparison of the results with regard to J-integral at initiation of stable crack, J_i, and J_R curves shows that under certain conditions the 0.2 mm saw cut (notch root radius ≤ ≤ 0.02 mm) is a useful alternative, if reproducible generation of a fatigue pre-crack will not be successful or too expensive. The tests were carried out on StE 460 and on a welded joint of this steel at 25 ± 2°C.     

Molecular computing: the lock-key paradigm

Molecular computers are natural or artificial systems in which macromolecules individually mediate critical information-processing functions. Biological organisms are the naturally occurring examples. Their information-processing virtuosity traces ultimately to the fact that macromolecules, most notably proteins, can recognize specific molecular objects in their environment in a manner that uses shape and depends sensitively on physiochemical context. The ultimate capabilities of this shape-based mode of computing and the technological implications that this mode may have are discussed. Basic principles of molecular computing are introduced and some ways that they might combine to yield new approaches to information technology are considered. Specifically, signal-integrating, optomolecular and neuromolecular computer architectures are described     

Vollständige Beschreibung der Spannungs-Dehnungs-Kurven mit Hooke-Gerade,Fließhorizontale und Verfestigungsklothoide

Es werden die experimentellen und numerischen Ergebnisse dargelegt, um die gesamte Spannungs-Dehnungs-Kurve des Zugversuches mit sechs Kennwerten zu beschreiben. Dies sind: Elastizitätsmodul, Streckgrenze, Fließdehnung, Zugfestigkeit, Gleichmaßdehnung und Verfestigungsmodul. Dadurch werden auch im überelastischen Bereich numerische Beziehungen möglich zwischen: Verformungen und Spannungen, Dehngrenzen, Tangenten-Modulen und Arbeitsvermögen. Die Beziehungen erweitern die Ermittlung von Last- und Eigenspannungen, und die Berechnungen beim plastischen Umformen, beim Traglastverfahren und beim Messen von Kerbspannungen.     

Quantitation of intrathecal measles virus IgG antibody synthesis rate: subacute sclerosing panencephalitis and multiple sclerosis

A method for quantitating specific anti-viral antibodies in serum and cerebrospinal fluid (CSF) is established using enzyme-linked immunosorbent assay (ELISA). Quantitated antibody levels are used to determine intrathecal specific IgG synthesis rate for the particular antibody. Measles virus was used as a model for validating this quantitative technique: a mutated form of measles virus is a cause of subacute sclerosing panencephalitis (SSPE) and there is a possibility that measles virus is related to the cause of multiple sclerosis (MS). Matched serum and CSF samples were assayed. Concentration of anti-measles IgG was determined and intrathecal measles-specific IgG synthesis rate was calculated. For the SSPE samples, measles-specific IgG synthesis rate was elevated and comprised > 20% of the total intrathecal IgG synthesis rate; these results are consistent with the literature. The ELISA method can be performed routinely, providing a quick, simple, reproducible means of quantitating specific antibody concentrations, with sensitivity greater than 1 nanogram per milliliter. With this method, quantitation of IgG antibodies to any other viral antigen can be reliably and precisely determined.     

High-level production and long-term storage of engineered antibodies in transgenic tobacco seeds

We have used transgenic tobacco seeds to produce large amounts of a functionally active engineered antibody. A gene infusion encoding an antigen-binding single chain Fv protein (scFv) that recognizes the hapten oxazolone was constructed and used as a model. After characterization in a bacterial expression system ,the scFv gene was cloned into a plant expression cassette conferring seed specific expression, and transferred using Agrobacterium-mediated transformation, into Nicotiana tabacum. The expressed scFv could be detected in the developing as well as ripe seeds of regenerated transgenic plants, and the functionally active scFv is stabaly deposited and accumulates up to 0.67% of the total soluble seed protein. After storage of ripe transgenic tobacco seeds for one year at room temperature there was no loss of scFv protein or its antigen-binding activity.     

Synthesis of corneal keratan sulfate proteoglycans by bovine keratocytes in vitro

Keratan sulfate proteoglycans (KSPGs) are the major proteoglycans of the cornea and are secreted by keratocytes in the corneal stroma. Previous studies have been able to show only transient secretion of KSPG in cell culture. In this study, cultures of bovine keratocytes were found to secrete the three previously characterized KSPG proteins into culture medium. Reactivity with monoclonal antibody I22 demonstrated substitution of these proteins with keratan sulfate chains. KSPG constituted 15% of the proteoglycan metabolically labeled with [35S]sulfate in keratocyte culture medium. This labeled KSPG contained keratan sulfate chains of 4700 Da compared to 21,000 Da for bovine corneal keratan sulfate. Labeled keratan sulfate from cultures contained nonsulfated, monosulfated, and disulfated disaccharides that were released by digestion with endo-beta-galactosidase or keratanase II. Nonsulfated disaccharides were relatively more abundant in keratan sulfate from culture than in corneal keratan sulfate. These results show that cultured bovine keratocytes maintain the ability to express all three of the known KSPG proteins, modified with keratan sulfate chains and sulfated on both N-acetylglucosamine and galactose moieties. KSPG made in vitro differs from that found in vivo in the length and sulfation of its keratan sulfate chains. The availability of cell cultures secreting corneal keratan sulfate proteoglycans provides an opportunity to examine biosynthesis and control of this important class of molecules.