Designed polyelectrolyte shell on magnetite nanocore for dilution-resistant biocompatible magnetic fluids.

Magnetite nanoparticles (MNPs) coated with poly(acrylic acid-co-maleic acid) polyelectrolyte (PAM) have been prepared with the aim of improving colloidal stability of core-shell nanoparticles for biomedical applications and enhancing the durability of the coating shells. FTIR-ATR measurements reveal two types of interaction of PAM with MNPs: hydrogen bonding and inner-sphere metal-carboxylate complex formation. The mechanism of the latter is ligand exchange between uncharged -OH groups of the surface and -COO(-) anionic moieties of the polyelectrolyte as revealed by adsorption and electrokinetic experiments. The aqueous dispersion of PAM@MNP particles (magnetic fluids - MFs) tolerates physiological salt concentration at composition corresponding to the plateau of the high-affinity adsorption isotherm. The plateau is reached at small amount of added PAM and at low concentration of nonadsorbed PAM, making PAM highly efficient for coating MNPs. The adsorbed PAM layer is not desorbed during dilution. The performance of the PAM shell is superior to that of poly(acrylic acid) (PAA), often used in biocompatible MFs. This is explained by the different adsorption mechanisms; metal-carboxylate cannot form in the case of PAA. Molecular-level understanding of the protective shell formation on MNPs presented here improves fundamentally the colloidal techniques used in core-shell nanoparticle production for nanotechnology applications

Heizungsautomatisierung Schlussbericht

Modern space HVAC systems are largely automated. In order to minimize energy consumption, attempts were made to develop a generalizable, innovative automation concept with self-learning, predictive and self-optimizing automation systems. This necessitates parallel automatic online process modelling and identification. Several modelling methods for experimental process analysis were programmed and investigated, and a preliminary selection was made. As a result, the multistage GMDH algorithm and the neuronal net were followed up, and the alpha-perceptron algorithm was analyzed and evaluatedModerne Anlagen der Heizungs-, Lueftungs- und Klimatechnik sind bereits hochgradig mit Automatisierungstechnik ausgeruestet. Als ein Beitrag zur Problemloesung mit Minimierung des Gesamtenergiebedarfs wurde der Entwurf eines moeglichst verallgemeinerungsfaehigen und damit uebertragbaren innovativen Automatisierungskonzeptes mit selbsteinstellenden, lernfaehigen, praediktiven und selbstoptimierenden Automatisierungseinrichtungen angesehen. Dazu ist eine schritthaltende, automatische On-line-Prozessmodellbildung und On-line-Identifikation erforderlich. Hierfuer wurden mehrere Modellierungsmethoden fuer die experimentelle Prozessanalyse programmiert und voruntersucht sowie hieraus eine Vorauswahl getroffen. In deren Ergebnis wurde der Mehrstufige GMDH-Algorithmus sowie das Neuronale Netz weiterverfolgt und zusaetzlich der Alpha-Perzeptron-Algorithmus naeher analysiert und kritisch bewertet. (orig.)SIGLEAvailable from TIB Hannover: F99B690 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman