Endothelial cell adhesion on polyelectrolyte multilayer films functionalised with fibronectin and collagen

The seeding of endothelial cells on biomaterial surfaces has become a major challenge to achieve better haemocompatibility of these surfaces. Multilayers of polyelectrolytes formed by the layerby-layer method are promising in this respect. In this study, the interactions of endothelial cells with multilayered polyelectrolytes films were investigated. The build-ups were prepared by selfassembled alternatively adsorbed polyanions and polycations functionalised with fibronectin and collagen. Anionic poly(sodium 4-styrenesulfonate) and cationic poly(allylamine hydrochloride) polyelectrolytes were chosen as a model system. Elaborated surfaces were characterised by electrochemical impedance spectroscopy and cyclic voltammetry. The modified electrode showed good reversible electrochemical properties and high stability in an electrolyte solution. The film ohmic resistance was highest when the film was coated with fibronectin; the parameters so determined were correlated with atomic force microscopy images. Cell colorimetric assay (WST-1) and immunofluorescence were used to quantify the cell viability and evaluate the adhesion properties. When cultured on a surface where proteins were deposited, cells adhered and proliferated better with fibronectin than with collagen. In addition, a high surface free energy was favourable to adhesion and proliferation (48.8 mJ m⁻² for fibronectin and 39.7 mJ m⁻² for collagen, respectively). Endothelial cells seeded on functionalised-polyelectrolyte multilayer films showed a good morphology and adhesion necessary for the development of a new endothelium.     

Bragg spectroscopy and Ramsey interferometry with an ultracold Fermi gas

We report on the observation of Bragg scattering of an ultracold Fermi gas of ⁶Li atoms at a dynamic optical potential. The momentum states produced in this way oscillate in the trap for time scales on the order of seconds, nearly unperturbed by collisions, which are absent for ultracold fermions due to the Pauli principle. In contrast, interactions in a mixture with ⁸⁷Rb atoms lead to rapid damping. The coherence of these states is demonstrated by Ramsey-type matter wave interferometry. The signal is improved using an echo pulse sequence, allowing us to observe coherence times longer than 100 μs. Finally, we use Bragg spectroscopy to measure the in-situ momentum distribution of the ⁶Li cloud. Signatures for the degeneracy of the Fermi gas can be observed directly from the momentum distribution of the atoms inside the trap.     

Influence of Vertical Vibrations on the Stability of a Binary Mixture in a Horizontal Porous Layer Subjected to a Vertical Heat Flux

Macroscale three-dimensional modeling of fluid flow in a thin porous layer under unsaturated conditions is a challenging task. One major issue is that such layers do not satisfy the representative elementary volume length-scale requirement. Recently, a new approach, called reduced continua model (RCM), has been developed to describe multiphase fluid flow in a stack of thin porous layers. In that approach, flow equations are formulated in terms of thickness-averaged variables and properties. In this work, we have performed a set of experiments, where a wet \(260\hbox {-}\upmu \hbox {m}\)-thin porous layer was placed on top of a dry layer of the same material. We measured the change of average saturation with time using a single-sided low-field nuclear magnetic resonance device known as NMR-MOUSE. We have employed both RCM and the traditional Richards equation-based models to simulate our experimental results. We found that the traditional unsaturated flow model cannot simulate experimental results satisfactorily. Very close agreement was obtained by including the dynamic capillary term as postulated by Hassanizadeh and Gray in the traditional equations. The reduced continua model was found to be in good agreement with the experimental result without adding dynamic capillarity term. Moreover, the computational effort needed for RCM simulations was one order of magnitude less than that of traditional models.     

Fluorometrische Mikrobestimmung des Galliums mit Dibromoxin

Zusammenfassung Das 5,7-Dibrom-8-hydroxychinolin eignet sich zur fluorometrischen Mikrobestimmung des Galliums, das vorher durch eine Äther-Salzsäuretrennung von den meisten übrigen Kationen getrennt werden muß, da eine Anzahl von Fremdionen fluoreszenzlöschend wirkt. Gegebenenfalls muß eine weitere mikroanalytische Isolierung des Galliums von solchen unerwünschten Begleitern ausgeführt werden, worüber an anderer Stelle berichtet wird 5,6. Gallium wird aus der vom Äther befreiten, schwach salzsauren Lösung mit Dibromoxin und Chloroform extrahiert und dann die Fluoreszenz des mit UV-Licht bestrahlten Galliumdibromoxinates in einem lichtelektrischen Fluorometer bestimmt. Der untersuchte Konzentrationsbereich liegt zwischen 0,25 und 1 g Ga in 6 ml CHCl₃.

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Summary 5,7-dibromo-8-hydroxyquinoline is well suited for the fluorometric micro determination of gallium. The latter should be separated previously, by ether extraction from a hydrochloric acid solution, from most of the other ions, because quite a few foreign ions quench the fluorescence. If necessary, a further microanalytical isolation of the gallium from such undesirable companions must be carried out; a report of this will be given elsewhere 5,6. The gallium is extracted with dibromo-hydroxyquinoline and chloroform from the weak hydrochloric acid solution after the ether is removed. The fluorescence of the gallium dibromo-oxinate is determined with a photoelectric fluorometer after irradiation with ultraviolet light. The concentration range studied ranged between 0.25 and 1 g gallium in 6 ml chloroform.

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Résumé Il est possible d'effectuer un microdosage fluorométrique du gallium à l'aide de la 5,7-dibromo 8-hydroxyquinoléine après sa séparation préalable par l'éther chlorhydrique de la plupart des autres cations, afin d'éviter leur éventuelle action extinctrice de la fluorescence. En présence de tels ions il est même quelquefois nécessaire de parfaire cette séparation par un isolement microanalytique du gallium; cette partie de la recherche sera publiée d'autre part 5,6. Le gallium est extrait par la dibromo-hydroxyquinoléine et le chloroforme de la solution faiblement chlorhydrique dont on a chassé l'éther et l'on détermine alors la fluorescence du dibromoxinate de gallium en lumière ultraviolette à l'aide d'un fluoromètre photoélectrique. Le domaine de concentrations étudié s'étend de 0,25 à 1 g de gallium en 6 ml de chloroforme.

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Herrn Prof. Dr.Robert Strebinger zum70. Geburtstag gewidmet.