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11.
Orentienė A Olšauskaitė V Vičkačkaitė V Padarauskas A 《Journal of chromatography. A》2011,1218(39):6884-6891
The potential of 1.7 μm ethylene bridged hybrid silica phase was investigated for the separation of twelve imidazolium-based ionic liquid cations. U-shaped retention profile was observed for all solutes with an increase in retention at both low and high acetonitrile content. Chromatographic behaviour of imidazolium cations in both hydrophilic interaction chromatography (HILIC) and per aqueous liquid chromatography (PALC) modes was studied by varying key parameters such as buffer concentration and pH, acid additive, organic modifier and column temperature. Experimental data provided some evidences that under PALC conditions cationic solutes are retained predominantly by mixed hydrophobic/ion-exchange interactions. In the HILIC mode, both partitioning and ion-exchange interactions are responsible for the retention of solutes. Compared to PALC, HILIC provided significantly higher efficiencies with less or even no peak tailing, better separation selectivity and greater resistance to overload. In PALC mode gradient elution was required to achieve adequate retentivity of all solutes but selectivity was not sufficient to distinguish between solutes with very similar hydrophobicity. In contrast, under HILIC conditions twelve solutes were almost completely resolved in less than 4 min by using isocratic elution. Summarizing, it could be concluded that ethylene bridged hybrid silica column providing a dual retention mechanism offers the possibility of selecting between the two retention modes with opposite separation selectivity, just by changing the composition of the mobile phase. 相似文献
12.
Moore CJ Retford CM Beck MJ Asta M Miksis MJ Voorhees PW 《Physical review letters》2006,96(12):126101
Recent experiments and calculations have highlighted the important role of surface-energy (gamma) anisotropy in governing island formation in the Ge/Si(001) system. To further elucidate the factors determining this anisotropy, we perform atomistic and continuum calculations of the orientation dependence of gamma for strained-Ge surfaces near (001), accounting for the presence of dimer-vacancy lines (DVLs). The net effect of DVLs is found to be a substantial reduction in the magnitude of the slope of gamma vs orientation angle, relative to the highly negative value derived for non-DVL, dimer-reconstructed, strained-Ge(001) surfaces. The present results thus point to an important role of DVLs in stabilizing the (001) surface orientation of a strained-Ge wetting layer. 相似文献
13.
Martin?Ma?ín Miroslav?KotrlaEmail author Bo?Yang Mark?Asta Mika O.?Jahma Tapio?Ala-Nissila 《The European Physical Journal B - Condensed Matter and Complex Systems》2013,86(8):359
We use a multiscale approach to study a lattice-gas model of submonolayer growth of Fe/Mo (110) by Molecular Beam Epitaxy. To begin with, we construct a two-dimensional lattice-gas model of the Fe/Mo (110) system based on our first-principles calculations of the monomer diffusion barrier and adatom-adatom interactions. The model is investigated by equilibrium Monte Carlo (MC) simulations to compute the diffusion coefficients of Fe islands of different sizes. These diffusion coefficients are used as input to the coarse-grained kinetic rate equation (KRE) approach. We also evaluate effects of the range of Fe-Fe interaction, restriction of interaction to third nearest neighbors allowed to develop feasible atomistic kinetic Monte Carlo (KMC) model. We calculate time evolution of the island size distributions by both KMC and KRE methods and find good agreement between the two methods. 相似文献
14.
Asta Ines Rekertait Aura Valinien Povilas Virbickas Arunas Ramanavicius 《Electroanalysis》2019,31(1):50-57
In this work, three types of electrodes suitable for amperometric glucose biosensors were designed. One type of electrode was based on bio‐selective layer of polypyrrole/(glucose oxidase)/(Prussian Blue) (Ppy/GOx/PB) and it was used as a control electrode regarding to which electrochemical properties of two other types of electrodes were compared. During the formation of Prussian blue layers graphite electrodes were additionally modified by Ni‐hexacyanoferrate (NiHCF) and by Co‐hexacyanoferrate (CoHCF) in order to design Ppy/GOx/PB‐NiHCF and Ppy/GOx/PB‐CoHCF electrodes, respectively. Some physicochemical characteristics of all three types of electrodes were evaluated and compared. The Ppy/GOx/PB‐NiHCF electrode showed wider linear range of the calibration curve than Ppy/GOx/PB and Ppy/GOx/PB‐CoHCF electrodes. The effect of temperature on analytical performance of the Ppy/GOx/PB‐NiHCF based biosensor has been evaluated and activation energy of enzyme catalysed reaction has been calculated within the temperature range of 15 °C to 30 °C. 相似文献
15.
Thin films containing both the azo-dye disperse red 1 (DR1) and the poly(methylmetacrylate) (PMMA) or the poly(phenylenevinylene) (PPV) are deposited by Langmuir-Blodgett and spin coating techniques on various substrates. The morphology, surface structure and growth pattern of the azo-dye-polymers were studied by atomic force microscopy. Nucleation and growth processes are responsible for the generation of different structures. The spin coated films were additionally oriented using the electric field poling method (corona poling). The film homogeneity is improved by this method in all cases. Due to the polar character of DR1 molecules, rod-like sub-structures are observed after the corona poling process in DR1-MMA films. The indium tin oxide surface enhances reorientation of the azo-dye-polymer molecules during corona poling and results in a significant reduction of the surface roughness. 相似文献
16.
Mateusz Kwitniewski Asta Juzeniene Li-Wei Ma Renata Glosnicka Alfreda Graczyk Johan Moan 《Journal of photochemistry and photobiology. B, Biology》2009,94(3):214-222
Photodynamic therapy (PDT) is an alternative treatment modality involving light activated drugs, called photosensitizers (PSs), to treat cancer and non-cancerous conditions. The search for new compounds which might become effective PSs is the major direction for PDT development. In the present work we have studied the dark toxicity, intracellular localization and photodynamic properties of four potential, water soluble, second generation PSs – PP(Arg)2, PP(Ser)2Arg2, PP(Ala)2Arg2, PP(Phe)2Arg2, all diamino acid derivatives of protoporphyrin IX. Human prostate cancer (DU-145) and squamous carcinoma (A431) cells were used as experimental model.Among investigated compounds PP(Ser)2Arg2 exhibited the lowest dark toxicity and the highest PDT effectiveness towards both cell lines. Fluorescence microscopy revealed the time-dependent changes in intracellular localization of the PS which were related to the phototoxicity. The results show that PP(Ser)2Arg2 may be a potential PS for PDT. 相似文献
17.
Chiara Dall’Asta Mattia Mangia Franz Berthiller Alexandra Molinelli Michael Sulyok Rainer Schuhmacher Rudolf Krska Gianni Galaverna Arnaldo Dossena Rosangela Marchelli 《Analytical and bioanalytical chemistry》2009,395(5):1335-1345
In this paper, the results obtained by five independent methods for the quantification of fumonisins B1, B2, and B3 in raw maize are reported. Five naturally contaminated maize samples and a reference material were analyzed in three different
laboratories. Although each method was validated and common calibrants were used, a poor agreement about fumonisin contamination
levels was obtained. In order to investigate the interactions among analyte and matrix leading to this lack of consistency,
the occurrence of fumonisin derivatives was checked. Significant amounts of hidden fumonisins were detected for all the considered
samples. Furthermore, the application of an in vitro digestion protocol to raw maize allowed for a higher recovery of native
fumonisins, suggesting that the interaction occurring among analytes and matrix macromolecules is associative rather than
covalent. Depending on the analytical method as well as the maize sample, only 37–68% of the total fumonisin concentrations
were found to be extractable from the samples. These results are particularly impressive and significant in the case of the
certified reference material, underlying the actual difficulties in ascertaining the trueness of a method for fumonisin determination,
opening thus an important issue for risk assessment. 相似文献
18.
Although the properties of crystal-melt interfaces have been extensively studied in pure materials, effects of alloying on the interfacial free energy remain relatively poorly understood. In this work we make use of Monte Carlo computer simulations for model binary Lennard-Jones alloys to explore the effects which variations in atomic-size mismatch and the chemical contributions to mixing energies have upon density and composition profiles, as well as the resulting magnitudes of equilibrium adsorption coefficients in concentrated alloys. We study four different model systems covering a range of chemical and size mismatch, finding relatively small adsorption values which are nevertheless statistically different from zero. 相似文献
19.
Juzeniene A Juzenas P Bronshtein I Vorobey A Moan J 《Journal of photochemistry and photobiology. B, Biology》2006,84(2):161-166
Cell survival was investigated after exposing cells in vitro to different temperatures before or after photodynamic therapy with 5-aminolevulinic acid. The photodynamic process was found to be temperature dependent. Cells exposed for 1h to 41 degrees C before light exposure or to 7 degrees C after light exposure showed decreased survival. Furthermore, the photobleaching rate of protoporphyrin IX in the cells was found to increase with increasing temperature during the light exposure. Thus, the photodynamic effect with 5-aminolevulinic acid may be enhanced by heating the tumour area before, and by cooling it immediately after the treatment. 相似文献
20.