Korrelation zwischen Rohdichte und Harzgehalt sowie Qualitätskennwerten bei Homogenplatten aus Bagasse

The aim of the present publication is, to serve with experiences being available with production of boards from bagasse as far as they can be transferred to other renewable raw materials. In order to achieve good comparability, only one variable was changed in each series of trials. To demonstrate the correlations with the density, the resin content was kept constant. In turns, to show the correlations with the resin content, the density was kept constant. Defibering the bagasse was done after drying, since the project was aiming for a board quality comparable to particleboard, only. Defibering bagasse before drying would also be possible without problems. A finer fiber is then achieved bringing the structure of board even closer to MDF. The results show clearly, that with bagasse the minimum requirements of DIN 68761/68763 for V20 boards can be achieved either with a lower density or alternatively with a lower binder content as compared with wood mixes predominantly employed in Europe. The cross section of bagasse board is a prominent distinctive mark as compared with wood particleboard. The structure of cross section of bagasse board comes closer to that of MDF than to particleboard. These results cannot be fully transferred to other monocotyledones. Bagasse is not fully lignified and owns consequently a higher plasticity than fully lignified fibres. As consequence, with fibres from other monocotyledons than bagasse, the necessity of slightly higher density or higher resin content can be expected. The homogeneity may also be slightly less favourable as with bagasse.     

Thermodynamically consistent algorithms for a finite‐deformation phase‐field approach to fracture

Phase‐field approaches to fracture offer new perspectives toward the numerical solution of crack propagation. In this paper, a phase‐field method for finite deformations and general nonlinear material models is introduced using a novel multiplicative split of the principal stretches to account for the different behavior of fracture in tension and compression. An energy‐momentum consistent integrator is developed and applied to the arising nonlinear coupled phase‐field model. This approach is thermodynamically consistent in the sense that the first law of thermodynamics if fulfilled with respect to the dissipation function. The capabilities and the performance of the proposed approach is demonstrated in several representative examples. Copyright © 2014 John Wiley & Sons, Ltd.     

A highly sensitive C-terminal specific radioimmunoassay for human parathormone as a routine method (author's transl)

The basis for the radioimmunoassay of parathormone (PTH) as a routine method is a new sheep antiserum and a labelled PTH stabilised by a modification of the purification technique. The antiserum is obtained by immunisation with pig and cattle parathormone, it is C-terminal specific and is used in the assay in a final dilution of 1:35000. The affinity to human PTH is markedly greater than of the antisera used up to now. Two purification steps of 125J labelled bovine PTH lead to a tracer with a nonspecific binding of approximately 5% which increases to approximately 10% within 6 weeks. All normal sera investigated so far were measurable quantitatively (normal range 0.7 to 2.5 mul/equiv.). The lower sensitivity range was at 0.3 mul/equiv. All patients with chronic renal insufficiency and dialysis patients have an increased PTH concentration (3.9 to greater than 20 mul/equiv.). This also applies to patients with primary hyperparathyroidism (2.9 to greater than 20 mul/equiv.).     

Transient 3d contact problems—NTS method: mixed methods and conserving integration

The present work deals with a new formulation for transient large deformation contact problems. It is well known, that one-step implicit time integration schemes for highly non-linear systems fail to conserve the total energy of the system. To deal with this drawback, a mixed method is newly proposed in conjunction with the concept of a discrete gradient. In particular, we reformulate the well known and widely-used node-to-segment methods and establish an energy-momentum scheme. The advocated approach ensures robustness and enhanced numerical stability, demonstrated in several three-dimensional applications of the proposed algorithm.     

Weak Cn coupling for multipatch isogeometric analysis in solid mechanics

The objective of this contribution is to design a novel methodology to enforce interface conditions preserving higher-order continuity across the interface. In recent years, isogeometric methods using NURBS as basis functions have gained increasing attention, especially in the context of higher-order partial differential equations. They require, in general, higher continuity across interfaces, and thus, new methodologies for domain decomposition constraints capable to deal with those requirements have to be developed. In this contribution, we introduce, in a first step, the coupling constraints using a Euclidean norm on the interface and construct new basis functions. A reformulation as saddle point system allows for a comparison with classical mortar approaches and leads finally to an extended mortar method to enforce Cⁿ continuity.     

Director‐based beam finite elements relying on the geometrically exact beam theory formulated in skew coordinates

In the present work, a new director‐based finite element formulation for geometrically exact beams is proposed. The new beam finite element exhibits drastically improved numerical performance when compared with the previously developed director‐based formulations. This improvement is accomplished by adjusting the underlying variational beam formulation to the specific features of the director interpolation. In particular, the present approach does not rely on the assumption of an orthonormal director frame. The excellent performance of the new approach is illustrated with representative numerical examples. Copyright © 2013 John Wiley & Sons, Ltd.     

Calculation of radioimmunochemical determinations by "spline approximation" (author's transl)

A simplified method, based on the "spline approximation", is reported for the calculation of the standard curves of radioimmunochemical determinations. It is possible to manipulate the mathematical function with a pocket calculator, thus making it available for a large number of users. It was shown that, in contrast to the usual procedures, it is possible to achieve optimal quality control in the preparation of the standard curves and in the interpolation of unknown plasma samples. The recaluculation of interpolated values from their own standard curve revealed an error of 4.9% which would normally be an error of interpolation. The new method was compared with two established methods for 8 different radioimmunochemical determinations. The measured values of the standard curve showed a weighting, and there was a resulting quality control of these values, which, according to their statistical evalution, were more accurate than those of the others models (Ekins et al., Yalow et al., (1968), in: Radioisotopes in Medicine: in vitro studies (Hayes, R. L., Goswitz, F.A. & Murphy, B. E. P., eds) USA EC, Oak Ridge) and Rodbard et al. (1971), in: Competitive protein Binding Assys(Odell, W. D. & Danghedy, W. H., eds.) Lipincott, Philadelphia and Toronto). In contrast with these other models, the described method makes no mathematical or kinetic preconditions with respect to the dose-response relationship. To achieve optimal reaction conditions, experimentally determined reaction data are preferable to model theories.     

An augmentation technique for large deformation frictional contact problems

The present work deals with a new approach to frictional large deformation contact problems. In particular, a new formulation of the frictional kinematics is introduced that is based on a specific augmentation technique used for the introduction of additional variables. This augmentation technique substantially simplifies the formulation of the whole system. A size reduction of the resulting system of algebraic equations is proposed. Consequently, the augmentation technique does not lead to an increase in size of the algebraic system of equations to be ultimately solved. The size reduction retains the simplicity of the formulation and preserves important conservation laws such as conservation of angular momentum. Copyright © 2013 John Wiley & Sons, Ltd.