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  • 1
    Electronic Resource
    Electronic Resource
    Quartz crystal microbalance investigation of the interaction of bacterial toxins with ganglioside containing solid supported membranes (1997)
    Springer
    European biophysics journal 26 (1997), S. 261-270 
    Details
    ISSN: 1432-1017
    Keywords: Key words Quartz crystal microbalance (QCM) ; Cholera toxin ; Tetanus toxin ; Pertussis toxin ; Solid supported membranes ; Gangliosides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The binding of cholera toxin, tetanus toxin and pertussis toxin to ganglioside containing solid supported membranes has been investigated by quartz crystal microbalance measurements. The bilayers were prepared by fusion of phospholipid-vesicles on a hydrophobic monolayer of octanethiol chemisorbed on one gold electrode placed on the 5 MHz AT-cut quartz crystal. The ability of the gangliosides GM1, GM3, GD1a, GD1b, GT1b and asialo-GM1 to act as suitable receptors for the different toxins was tested by measuring the changes of quartz resonance frequencies. To obtain the binding constants of each ligand-receptor-couple Langmuir-isotherms were successfully fitted to the experimental adsorption isotherms. Cholera toxin shows a high affinity for GM1 (Ka = 1.8 ⋅ 108M–1), a lower one for asialo-GM1 (Ka = 1.0 ⋅ 107 M–1) and no affinity for GM3. The C-fragment of tetanus toxin binds to ganglioside GD1a, GD1b and GT1b containing membranes with similar affinity (Ka∼106 M–1), while no binding was observed with GM3. Pertussis toxin binds to membranes containing the ganglioside GD1a with a binding constant of Ka = 1.6 ⋅ 106 M–1, but only if large amounts (40 mol%) of GD1a are present. The maximum frequency shift caused by the protein adsorption depends strongly on the molecular structure of the receptor. This is clearly demonstrated by an observed maximum frequency decrease of 99 Hz for the adsorption of the C-fragment of tetanus toxin to GD1b. In contrast to this large frequency decrease, which was unexpectedly high with respect to Sauerbrey's equation, implying pure mass loading, a maximum shift of only 28 Hz was detected after adsorption of the C-fragment of tetanus toxin to GD1a.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002490050079
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  • 2
    Electronic Resource
    Electronic Resource
    Macroscopic pressure–volume–temperature properties versus free-volume characteristics of isotropic pressure-densified amorphous polymer glasses (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 11095-11106 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We made a series of isotropic pressure-densified (0–200 MPa) amorphous homopolymer [atactic polystyrene (a-PS)] and copolymer [poly(styrene-co-acrylonitrile) (SAN) and poly(styreneco-maleic anhydride) (SMA)] glasses and studied their macroscopic pressure–volume–temperature (PVT) properties vs their free-volume characteristics from the Simha–Somcynsky equation-of-state (EOS) theory and from positron annihilation lifetime spectroscopy (PALS). The glass densities lie in the range of 1.0403–1.0535 g/cm3 (PS), 1.0573–1.0759 g/cm3 (SAN), and 1.0989–1.1196 g/cm3 (SMA). With increasing formation pressure, all pressure-densified glasses exhibit decreasing volume and free-volume characteristics such that the changes in specific volume (1.26%–1.85%) are 〈ortho-positronium (o-Ps) lifetime τ3 (5.5%–9.1%) 〈free-volume hole size V(τ3) (10.3%–17.1%) 〈free-volume fraction h (25.1%–30.5%). We find, furthermore, that the o-Ps formation probability I3 is independent of formation pressure. Likewise, the glasses' thermal expansivity α0 remains constant. There is a one-to-one correlation of τ3 and of I3 when calculated from POSITRONFIT and the maximum entropy lifetime (MELT) program. The full width at half maximum of free-volume distributions determined from PALS data and MELT does not change with formation pressure within established limits of uncertainty. Neither h vs V(τ3) nor h vs bulk modulus K, calculated from the Tait EOS of the glasses, show unique relations that are common to all the studied glasses. On the other hand, K vs V(τ3) gives a universal curve for all pressure-densified glasses from this study and from our previous study on PMMA: K=8.190–4.479×10−2V(τ3) (r2=0.92). Moreover, three more polymers from the literature are well described by this curve. The bulk moduli increase by up to 11.5% (PMMA), 7.6% (PS), 11.2% (SAN), and 10.2% (SMA) and they follow the order PS〈SMA〈SAN〈PMMA. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481748
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  • 3
    Electronic Resource
    Electronic Resource
    Using an ANN-approach for analyzing focus groups (2001)
    Bingley : Emerald
    Qualitative market research 4 (2001), S. 100-112 
    Details
    ISSN: 1352-2752
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Economics
    Notes: Explores the appropriateness of quantifying focus group discussions. Basic problems involved in quantification of text are addressed. Prior approaches are discussed and briefly evaluated. A new neural network algorithm for analyzing excerpts from in-depth interviews is presented. Keywords (brand names, values, etc.) are identified by the analyst. The entire text is scanned and a "covariance" matrix with weights expressing pairwise associations between words is established. This matrix can be used as input data set for advanced statistical analysis. The small illustrative study involves a focus group dealing with a holiday cruise. Results are inspected using multivariate analysis. Findings seem to make good sense. It is doubtful, though, that quantitative techniques will replace well-established qualitative approaches. On the contrary, quantitative methods for textual analysis may supplement and improve insight gained from qualitative scrutiny. Recommendations for future research are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/13522750110388590
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  • 4
    Electronic Resource
    Electronic Resource
    Spark Plasma Sintering Effect on the Decomposition of MgH2 (2005)
    Oxford, UK : Blackwell Science Inc
    Journal of the American Ceramic Society 88 (2005), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Spark plasma sintering (SPS) is one of the advanced consolidation techniques developed in the last few decades. We have studied the decomposition behavior of MgH2 and MgH2/graphite 1:1 mixtures in the SPS process. The standard SPS setup chosen was modified by including the temperature measurement inside the sample, so that the data can be compared with findings from thermal analysis. The results show clearly the reduction of the decomposition temperature measured in the SPS process if the necessary conditions (sufficient current density by applying the insulation) are realized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1551-2916.2005.00358.x
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  • 5
    Electronic Resource
    Electronic Resource
    Pressure-volume-temperature properties and free volume parameters of PEO/PMMA blends (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1061-1080 
    Details
    ISSN: 0887-6266
    Keywords: polymer blends ; dilatometry ; free volume ; specific volume ; excess volume ; compressibility ; thermal expansivity ; equation of state ; scaling parameters ; crystallinity ; glass transition ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Melt-miscible polymer blends of poly(ethylene oxide)/atactic poly(methyl methacrylate (PEO/a-PMMA)) were prepared by melt-mixing and characterized by pressure-volume-temperature (PVT) dilatometry in the pressure and temperature range of 0 to 200 MPa and 20 to 200°C, respectively. The PVT data were analyzed in terms of two equations of state (EOS). The empirical Tait EOS was applied in the glassy, semicrystalline, and equilibrium melt state, and the Simha-Somcynsky EOS theory was applied in the equilibrium melt and glassy state. The Simha-Somcynsky EOS theory contains a free volume function. The temperature, pressure, and composition dependence of the free volume fraction h calculated from the Simha-Somcynsky EOS theory was studied. As a function of blend composition we observe that the free volume fraction, thermal expansivity, and compressibility all deviate mainly positively from linearity while the specific volume deviates mainly negatively from linearity. These findings are reconciled with composition-dependent free volume parameters, the free volume and cell volume as well as with self- and cross-interaction parameters derived from the Simha-Somcynsky EOS theory as applied to polymer mixtures. Moreover, the pressure dependence of glass and melting transitions as well as crystallization kinetics have been investigated. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1061-1080, 1998
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
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