Study of the reciprocal space image of the biaxial nematic phase in the plane of the amphiphilic bilayer

High resolution synchrotron X-ray measurements have been performed on the uniaxial and biaxial phases of the lyotropic mixture potassuim laurate, decanol and water. An elegant magnetic orientational procedure allows us to obtain the cut of the reciprocal space image of the biaxial phase at the plane perpendicular to the amphiphilic bilayer. The analysis of densitometric profiles of the diffracted bands indicate an anisotropic micellar correlation in the plane of the amphiphilic bilayer. It is suggested that an anisotropic distribution of decanol and potassium laurate in this plane could be responsible for this effect.     

Interfacial cross-linking polymerisation process in oil/water emulsions

Summary We have studied the effect on the water-oil interfacial tension of a series of diacrylate molecules solubilized in the oil phase. Due to the weak tensio-active behaviour of these compounds, we have verified that the oil in water emulsions of this system were unstable. We have shown that these emulsions can be stabilized by polymerisation of the diacrylic molecules and that this process is essentially a surface cross-linking polymerisation.

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Zusammenfassung Es wurde der Einfluß einer Reihe von Diacrylaten, die in der Ölphase solubilisiert waren, auf die WasserÖl-Grenzflächenspannung untersucht. Es konnte nachgewiesen werden, daß die Öl-in-Wasser-Emulsionen instabil sind, was der geringen Grenzflächenaktivität dieser Systeme entspricht. Es wurde weiter gezeigt, daß diese Emulsionen stabilisiert werden können durch Polymerisation der Diacrylate. Dieser Prozeß ist eine Oberflächen-Vernetzungs-Polymerisation.

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Work partially supported by D. R. M. E. under contract number 73.34.099.

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With 1 figure and 4 tables     

Evaluation of molten inorganic salt hydrates as reaction medium for the derivatization of cellulose

Molten inorganic salt hydrates are highly efficient solvents forcellulose. The carboxymethylation of the polymer dissolved in this new group ofcellulose solvents was investigated. The homogeneous carboxymethylation ofcellulose in molten LiClO₄3H₂O using sodiummonochloroacetate in the presence of NaOH is possible. The formation of CMC wasconfirmed by FT- Raman spectroscopy. Structure analysis by means of HPLC afterchain degradation showed the formation of CMC with a DS of 2 after a shortreaction time of 4 h. The derivatives exhibit a statisticaldistribution of substituents along the polymer chain if prepared in moltenLiClO₄3H₂O as solvent. A substituent distributioninthe order C-6 > C-2 C-3 for anhydroglucose units (AGU) was concludedfrom ¹H-NMR measurements. The synthesis of CMC in the swellingmediumLiClxH₂O (2 x 5) yields polymers with astatistical distribution of functional groups along the chain. The watercontentof the salt melts has a dramatic influence on the DS_CMC.     

Stable cellulose nanospheres for cellular uptake

Pure, perfectly spherical cellulose nanoparticles with sizes of ≈80-260 nm can be prepared by dialysis starting from trimethylsilylcellulose (TMSC). The aqueous suspensions obtained are storable for several months. Subsequent covalent labeling of the cellulose nanoparticles with FITC has no influence on particle size, shape, and stability. The particles can be sterilized and suspended in biological media without structural changes. Incorporation of FITC-labeled cellulose nanoparticles into living human fibroblasts is studied using confocal LSM. In contrast to cellulose nanocrystals, fast cellular uptake is found for the nanospheres without transfection reagents or attachment of a receptor molecule. This suggests an influence of the geometry of biocompatible nanomaterials on endocytosis.     

Semi-synthetic polysaccharide sulfates as anticoagulant coatings for PET, 1--cellulose sulfate

In the present study, blood-compatible PET surfaces were prepared by coating with anticoagulant cellulose sulfates that were synthesized homogeneously in ionic liquids. The adsorption behavior of polysaccharides on PET films was investigated using QCM-D. It was demonstrated that pre-coating with different amino-group-containing polysaccharides improves the affinity toward cellulose sulfate. Moreover, the effect of different degrees of sulfation on the adsorption process was evaluated. Based on these results, several layer-by-layer coated PET foils were prepared that showed significantly improved blood compatibility compared to the initial untreated material.     

Elektrometrie

Ohne Zusammenfassung     

Charakterisierung der Endomorphismenringe endlicher abelscher Gruppen

Ohne Zusammenfassung     

Time-resolved imaging of fluorescent inclusions in optically turbid medium — phantom study

We present results of application of a time-resolved optical system for imaging of fluorescence excited in an inclusion containing indocyanine green (ICG), and located in optically turbid medium. The developed imaging system enabled simultaneous acquisition of fluorescence and diffusive reflectance. Eight independent time-resolved measurement channels based on time-correlated single photon counting technique were applied. In four of these channels, used for the fluorescence detection, sets of filters were applied in order to block the excitation light. Fast optomechanical switches allowed us to illuminate sequentially nine different spots on the surface of the studied object and finally 4×4 pixels maps at excitation and emission wavelengths were obtained. A liquid phantom used in this study consists of the fish tank filed with a solution ofmilk and water with black ink added to obtain optical properties in the range of the optical properties typical for the living tissue. A gel ball of a diameter of 5 mm with precisely controlled concentration of ICG was immersed in the liquid. The measurements were performed for inclusion located at different depths and for various ICG concentrations in the gel ball and in the surrounding liquid. The recorded distributions of times of arrival (DTA) of fluorescence photons and times of flight (DTOF) of diffusely reflected photons were analyzed by calculation of their statistical moments. We observed specific changes in moments of the measured DTAs as a function of depth of immersion of the fluorescent inclusion in the medium. We noted also that the changes of moments depend significantly on concentration of the dye in the fluorescence inclusion as well as in the surrounding liquid.     

Advantages of fluorescence over diffuse reflectance measurements tested in phantom experiments with dynamic inflow of ICG

Time-resolved measurements of diffuse reflectance and fluorescence were carried out using phantom with dynamic inflow of indocyanine green (ICG) in tubes located at different depths. Better sensitivity of fluorescence signals related to the inflow of the dye was observed in comparison to simultaneously acquired diffuse reflectance. Obtained results can be referred to results of in-vivo measurements. We have observed much larger amplitude of changes in relative number of detected photons, mean time of flight and variance of the distributions of times of arrival of fluorescence photons than amplitudes of respective parameters measured from diffuse reflectance distributions of times of flight of photons. The constructed phantom allows us to study influence of concentration of the dye in the tube and the surrounding medium as well as temporal relation between appearance of the boli in deeper and superficial tube. Results of the study were used in optimization of the time-resolved multichannel system for simultaneous monitoring of fluorescence and reflectance.