Stochastic response of hysteretic systems

This paper deals with approximate stochastic response of hyseretic structures under white noise excitation, based on It stochastic differential equations. Instead of the original system an equivalent nonlinear system is considered, in which the drift vector is given by a series expansion of the order n 1 in terms of the state variables. n = 1 represents the well-known case of equivalent linearization. Components in the drift vector representing the nonanalytical constitutive equations are replaced by a cubic polynomial expansion. The hierarchy of statistical moment equations is closed by a cumulant neglect closure scheme. The method has been applied to a bilinear single degree-of-freedom system subjected to white noise excitation, for which an equivalent system with a cubic series expansion to the constitutive equation is considered. The results obtained are compared with those of numerical simulation and alternative methods, and they provide substantial improvements compared to equivalent linearization.     

Liquefaction,Saccharification and Isomerization of Starches from Sources Other than Maize

Examination of the suitability of a number of starches for the production of fructose syrup is described. In addition to maize starch, starch from wheat, potatoes and tapioca has been examined. Liquefaction, saccharification and purification were performed in pilot scale, whereas the produced syrups were isomerized in laboratory scale. The liquefactions were performed with Termamyl® in a jet cooker process. Saccharification with Amyloglucosidase Novo 150 L under standard conditions gave good DX values. After purification the syrups were isomerized in laboratory columns with Sweetzyme®. The results - activity and productivity of Sweetzyme - were for all syrups as good as or better than those obtained with dextrose solutions.     

Accumulation of magnetic iron oxide nanoparticles coated with variably sized polyethylene glycol in murine tumors

Iron oxide nanoparticles have found widespread applications in different areas including cell separation, drug delivery and as contrast agents. Due to water insolubility and stability issues, nanoparticles utilized for biological applications require coatings such as the commonly employed polyethylene glycol (PEG). Despite its frequent use, the influence of PEG coatings on the physicochemical and biological properties of iron nanoparticles has hitherto not been studied in detail. To address this, we studied the effect of 333-20,000 Da PEG coatings that resulted in larger hydrodynamic size, lower surface charge, longer circulation half-life, and lower uptake in macrophage cells when the particles were coated with high molecular weight (M(w)) PEG molecules. By use of magnetic resonance imaging, we show coating-dependent in vivo uptake in murine tumors with an optimal coating M(w) of 10,000 Da.