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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 124 (1999), S. 89-99 
    ISSN: 1432-1106
    Keywords: Key words Microglial culture ; Brain macrophages ; Isolectin ; Ultrastructure ; Intracellular pathway
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The present study examined the lectin labeling of diverse morphological forms of microglia in culture. Similar to amoeboid microglial cells in vivo, polymorphic microglia showed lectin labeling at their plasma membranes, as well as in a few cytoplasmic vesicles and vacuoles. This labeling pattern was observed in cultured microglia incubated with isolectin at 4°C for 30 min. Five minutes after the temperature was raised to 37°C, the surface lectin receptors appeared to be internalized, as shown by the occurrence of many subsurface lectin-labeled vesicles, vacuoles and tubule-like structures. With longer incubation (up to 1–2 h at 37°C), many lysosomes and a few trans-Golgi saccules and associated lysosome-like structures became labeled. Concomitant with these changes was a reduction of lectin labeling at the plasma, with labeling having vanished in most of the cells after 1–2 h of incubation. By 24 h, only a few cells retained surface lectin labeling. It appears, therefore, that irrespective of morphology, lectin labeling (including its intracellular pathway) of microglia in culture parallels that of amoeboid microglia in vivo. This would offer a useful model for the study of lectin turnover in microglia and help to explain the roles of such receptors in microglial differentiation and function.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1629-1636 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Grafting of maleic anhydride (MAH) onto ethylene-propylene rubber (EPR) of apppoximately unitary ethylene/propylene molar ratio was performed by melt mixing in a laboratory-scale internal mixer with the addition of dicumyl peroxide (DCP) as an initiator. Concurrent with the graft reaction, the simultaneous presence of DCP and MAH enhanced the cross-linking of EPR chains as suggested by the emergence of a cure peak in the mixing torque, curve and supported by dynamic rheological evidence; the DCP-induced chain scission, however, remained important. The height of the cure peak increased consistently with the amounts of DCP and MAH in the reaction mixture. At the end of ca. 30 min of melt mixing, the gel content (determined via xylene extraction) of the functionalized EPR increased with the height of cure peak but then levelled off in the vicinity of ca. 50 wt%. The limited gel content was attributed to the competition from DCP-initiated scission reaction. This competition resulted in a wide distribution of chain connectivity, ranging from highly degraded short chains to partially cross-linked chains. At low DCP levels, the extent of grafting (estimated by means of Fourier-transform infrared spectroscopy) increased with the MAH content and then remained at a plateau value; at higher DCP levels, the plateau appeared to have already been reached even at the lowest MAH content (i.e., 0.5 phr) here. The limited extent of grafting was attributed to the immiscible nature and the low diffusion rate of MAH in EPR.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 30 (1990), S. 511-518 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Blends of polypropylene (PP) and ethylene-propylene rubber (EPR) and blends of polystyrene (PS) and styrene-butadiene rubber (SBR) were prepared in a laboratory-scale internal mixer at various blend compositions and rotor rates. Blend morphology was studied by means of electron microscopy. For each blend pair under the given processing conditions, the phase inversion process occurred progressively with respect to the variation in blend composition; it is within this composition range of phase inversion that dual-phase continuity was observed. In addition, Characteristic torque values of blends were found to deviate negatively from a linear additivity rule; the composition range of maximum deviation from linear additivity corresponded approximately to the composition range where dual-phase continuity was observed. Sperling's predictive scheme was found to yield acceptable (although not completely satisfactory) estimates for compositions of dual-phase continuity in the present systems. It was also observed that partial cross-linking of SBR during the mechanical blending process, as suggested by the appearance of a cure peak in the torque curve and supported by infrared spectroscopic evidence, resulted in morphological features drastically different from those of the uncured blends.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 19 (1987), S. 975-996 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal decomposition of acetylene has been studied in the temperature and pressure regimes of 1900-2500 K and 0.3-0.55 atm using a shock tube coupled to a time-of-flight mass spectrometer. A series of mixtures varying from 1.0-6.2% C2H2 diluted in a Ne-Ar mixture yielded a carbon atom density range of 0.24-2.0 × 1017 atoms cm-3 in the reflected shock zone. Concentration profiles for C2H2, C4H2, and C6H2 were constructed during typical observation times of 750 μs. C8H2 and trace amounts of C4H3 were found in relatively low concentrations at the high-temperature end of this study. A mechanism for acetylene pyrolysis is proposed, which successfully models this work and the results obtained by several other groups employing a variety of analytical techniques. Two values of the heat of formation for C2H(134 ± 2 and 127 ± 1 kcal/mol) were employed in the modeling process; superior fits to the data were attained using the latter value. The initial step of acetylene decomposition involves competition between two channels. In mixtures (〈200 ppm) where the acetylene concentrations are less than 2.18 × 10-9 mol cm-3, the decay is predominantly first order with respect to C2H2; in mixtures 〉200 ppm, the dominant initial step is second order. The rate constant for the second-order reaction is described by the equation \documentclass{article}\pagestyle{empty}\begin{document}$$ k = 2 \times 10^{13} \exp\, {\rm }(- 44.5{\rm\, kcal/}RT){\rm cm}^{\rm 3}\, {\rm mol}^{{\rm - 1}} {\rm s}^{{\rm - 1}} $$\end{document}Benzene concentrations predicted by the model are below the TOF detectability limit. C4H3 was observed in the 6.2% C2H2 mixture in accordance with the proposed mechanism.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 17 (1985), S. 225-253 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The high temperature pyrolysi of 1,3-butadiene has been investigated in the shock tube with two time-resolved diagnostic techniques: laser schlieren measurements of density gradient with 1, 2, 4, and 5% C4H6 in Ar or Kr, 0.26 〈 P2 〈 0.66 atm, over 1550-2200 K, and time-of-flight mass spectra for 3% C4H6-Ne, P5 ∼ 0.4 atm, 1400-2000 K. When combined with a recent single-pulse shock tube product analysis covering 1050-2050 K, these measurements permit a complete modeling of major species in C4H6 pyrolysis. Extrapolated density gradients and product analyses show initiation is dominated by C4H6 → 2C2H3., significant falloff and Arrhenius curvature being seen in the derived rates. A restricted rotor, Gorin model RRKM fit to these rates with reasonable parameters generates \documentclass{article}\pagestyle{empty}\begin{document}$$ k_\infty = 4.1 \times 10^{16} {\rm exp(} - 47000/{\rm T)s}^{ - 1},{\rm 1600} - 1900{\rm K}{\rm .} $$\end{document} The derived barrier, ΔH0º = 99 ± 4 kcal/mol, translates to ΔHfº,298 = 63.4 ± 2 kcal/mol for the heat of formation of vinyl radical. A mechanism for the formation of all products detected in the above experiments is given, together with a successful but semiquantitative kinetic model for major products. The measurements require the rate of vinyl radical dissociation, C2H3 + M → C2H2 + H + M, to be extremely low, k 〈 109 cm3/mol s for 1600 K, so that the dominant chain carrier in C4H6 pyrolysis is vinyl radical.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 20 (1988), S. 731-747 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal decomposition of 1,2 butadiene has been studied behind reflected shock waves over the temperature and total pressure ranges of 1300-2000 K and 0.20-0.55 atm using mixtures of 3% and 4.3% 1,2 butadiene in Ne. The major products of the pyrolysis are C2H2, C4H2, C2H4, CH4 and C6H6. Toluene was observed as a minor product in a narrow temperature range of 1500-1700 K. In order to model successfully the product profiles which were obtained by time-of-flight mass spectrometry, it was necessary to include the isomerization reaction of 1,2 to 1,3 butadiene. A reaction mechanism consisting of 74 reaction steps and 28 species was formulated to model the time and temperature dependence of major products obtained during the course of decomposition. The importance of C3H3 in the formation of benzene is demonstrated.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Propellants, Explosives, Pyrotechnics 11 (1986), S. 10-15 
    ISSN: 0721-3115
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The thermal analysis technique was used to rapidly evaluate the compatibility of explosives with contacted materials. The three kinetic parameters viz. activation energy E, reaction order n and pre-exponential factor A were calculated from three characteristic temperatures of a single DTA curve. The compatibility was evaluated from the four parameters E, n and the characteristic temperatures Tm (peak maximum) and To (decomposition starting point on the DTA curve). The results are compared to those obtained from the gasometric method.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 15 (1994), S. 278-288 
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This work presents methods to measure and analyze in-plane permeabilities of various fabric reinforcements. The principal flow directions need to be determined first by conducting flow visualization. From the flow front pattern, the ratio of the permeabilities in the two principal directions can be determined. The pressure and the flow rate relationship from both radial and unidirectional flow measurement methods are then used to calculate the values of the permeabilities. By the use of the unidirectional flow measurement method, the edge flow effect can also be estimated.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 8 (1976), S. 765-776 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Measurements of hydroxyl radical (HO) concentrations in ambient air by the technique of laser-induced fluorescence have been recently reported. The present study was undertaken to provide an independent test of the validity of those measurements. A photochemical reactor was used to provide a source of HO, and the concentration of HO in the reactor was determined by the laser-induced fluorescence technique. The HO concentration was also deduced from measured hydrocarbon decay rates in the reactor. There was agreement between the HO concentrations obtained by these two different methods, thus providing further validation of the fluorescence method. Some studies of HO fluorescence efficiency as well as of possible interferences with the fluorescence measurements are reported.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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