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Drescher S.,Martin Luther University of Halle Wittenberg | Meister A.,Center for Structure and Dynamics of Proteins | Garamus V.M.,German Center for Materials and Coastal Research | Hause G.,Biocenter | And 3 more authors.
European Journal of Lipid Science and Technology | Year: 2014

The synthesis of two symmetric single-chain phenylene-modified bolaamphiphiles with meta and ortho phenyl substitution pattern is described. The aggregation behavior of both bolaamphiphiles in aqueous suspension was investigated by differential scanning calorimetry (DSC), transmission electron microscopy (TEM), Fouriertransform IR (FTIR) spectroscopy, and small angle neutron scattering (SANS).We could show that a change in the substitution pattern from para to meta or ortho leads to a change in the aggregation behavior so that small micelles instead of nanofibers are formed. Furthermore, themixing behavior of these bolaamphiphileswith classical bilayer forming phospholipids, such as 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-distearoylsn- glycero-3-phosphocholine (DSPC) was studied by means of DSC, TEM, cryo-TEM, and small angle X-ray scattering (SAXS). The aim was to stabilize bilayermembranes formed by classical phospholipids by incorporation of bolaamphiphiles to obtain liposomes with improved stability suitable for drug delivery purposes. We could show that the phenylene-modified bolaamphiphiles are indeedmiscible with DPPCandDSPC; however, closed vesicles as observed for pure DPPC and DSPC were not found. Instead, small disk-like aggregates are formed. In the case of mixtures of phenylene-modified bolaamphiphiles with DPPC, these bilayer disks have a higher DSC transition temperature compared to pure DPPC indicating an increased stability of the ordered gel phase inside the disks. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Li Z.,Northeastern University China | Zou N.,Northeastern University China | Yang B.,Northeastern University China | Gan W.,German Center for Materials and Coastal Research | And 9 more authors.
Journal of Alloys and Compounds | Year: 2016

In this study, the influences of uniaxial compressive load on martensitic transformation from austenite to 5M martensite were studied in a directionally solidified Ni-Mn-Ga polycrystalline alloy with coexisting <0 0 1>A and <1 1 0>A preferred orientations parallel to the solidification direction (SD). Based on the neutron diffraction, the direct evidence on the variant redistribution induced by the thermal-mechanical treatment was presented and the selection of preferential variants was found to be strongly dependent on the austenite orientation. For the austenite with a <0 0 1>A preferred orientation, the compressive loading direction (LD) along the SD can promote the formation of preferred variants with {0 2 0}5MτSD (LD). On the other hand, for the austenite with a <1 1 0>A preferred orientation, the variants with {1 2 5}5M/{1¯ 2 5}5MτSD (LD) are more favorable after the thermal-mechanical treatment. Such variant selection is originated from the accommodation between the anisotropic lattice distortion in martensitic transformation and the external constraint. The present investigations may offer some fundamental information on variant selection subject to external stress field and the necessary guidelines for microstructure optimization of polycrystalline Ni-Mn-Ga alloys through external field training. © 2016 Elsevier B.V. All rights reserved. Source

Klein M.,TU Dortmund | Kuhlmann F.,TU Dortmund | Wittke P.,TU Dortmund | Dieringa H.,German Center for Materials and Coastal Research | Walther F.,TU Dortmund
Materials and Corrosion | Year: 2014

The corrosion behavior as well as the microstructure in initial state and after corrosive deterioration were investigated for the newly developed Mg-Al-Ba-Ca alloy DieMag422. In order to investigate the corrosion behavior, potentiodynamic polarization measurements and immersion tests were performed in different NaCl concentrations. The microstructure was observed using light microscopy and combined SEM and EDX studies of the specimens before and after corrosive deterioration. Potentiodynamic polarization measurements and immersion tests showed that DieMag422 has a strong susceptibility to corrosion in NaCl solutions. Light microscope and SEM studies revealed that the difference in the corrosion behavior can be attributed to the different occurrence of the anodic a-Mg phase and the cathodic Ca-rich phase. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Riabtseva A.,Lviv Polytechnic | Mitina N.,Lviv Polytechnic | Grytsyna I.,Ukrainian Academy of Sciences | Boiko N.,Ukrainian Academy of Sciences | And 4 more authors.
European Polymer Journal | Year: 2016

Branched polymeric surfactants composed of grafted non-ionic polyethylene glycol (PEG) and anionic polyelectrolyte chains were synthesized via radical polymerization initiated by the comb-like PEG-containing polyperoxide. Above definite concentration in solution, these surfactants form micelle-like structures (MLS). The MLS formed by branched polymeric molecules are of larger size in comparison with size of MLS formed by the initial PEG-containing polyperoxide that is caused mainly by different mechanism of their self-organization and morphology of formed MLS. The availability of grafted polyelectrolyte chains in the MLS provides a possibility of their use as the containers for immobilization of bio-active substances and nucleation of the inorganic nanoparticles, as well as formation of their stable colloidal systems in water in a wide pH range. Noticeable compaction and narrowed size distribution of the MLS were revealed after immobilization of doxorubicin (Dox) molecules or Fe2O3 nanocrystals. MLS-based systems were used for delivery of Dox and maghemite particles at treatment of tumor cells. Both MLS-based formulations of Dox and Fe2O3 were efficiently engulfed by rat glioma C6 cells. A significant (10 times) decrease in the effective therapeutic dose of Dox was found when this drug was delivered by a MLS-based formulation of Dox. That effect might be explained by a specific structure and functionality of the novel carrier used for immobilization of drug that should be delivered to target cells. © 2016 Elsevier Ltd. All rights reserved. Source

Li Z.,Northeastern University China | Zhang Y.,CNRS Study of Microstructures, Mechanics and Material Sciences lab | Zhang Y.,University of Lorraine | Esling C.,CNRS Study of Microstructures, Mechanics and Material Sciences lab | And 5 more authors.
Applied Physics Letters | Year: 2014

The influences of uniaxial compressive stress on martensitic transformation were studied on a polycrystalline Ni-Mn-Ga bulk alloy prepared by directional solidification. Based upon the integrated in-situ neutron diffraction measurements, direct experimental evidence was obtained on the variant redistribution of seven-layered modulated (7M) martensite, triggered by external uniaxial compression during martensitic transformation. Large anisotropic lattice strain, induced by the cyclic thermo-mechanical treatment, has led to the microstructure modification by forming martensitic variants with a strong 〈0 1 0〉7M preferential orientation along the loading axis. As a result, the saturation of magnetization became easier to be reached. © 2014 AIP Publishing LLC. Source

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