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  • 1
    Electronic Resource
    Electronic Resource
    Autoreceptor Regulation of Glutamate and Aspartate Release from Slices of the Hippocampal CA1 Area (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 56 (1991), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Slices of hippocampal area CA1 were employed to test the hypothesis that the release of glutamate and aspartate is regulated by the activation of excitatory amino acid autoreceptors. In the absence of added Mg2+, N-methyl-D-aspartate (NMDA)-receptor antagonists depressed the release of glutamate, aspartate, and γ-aminobutyrate evoked by 50 mMK+. Conversely, the agonist NMDA selectively enhanced the release of aspartate. The latter action was observed, however, only when the K+ stimulus was reduced to 30 mM. Actions of the competitive antagonists 3-[(±)-2-carboxypiperazin-4-yl]-propyl-1-phosphonic acid (CPP) and D-2-amino-5-phosphonovalerate (D-AP5) differed, in that the addition of either 1.2 mM Mg2+ or 0.1 μM tetrodotoxin to the superfusion medium abolished the depressant effect of CPP without diminishing the effect of D-AP5. These results suggest that the activation of NMDA receptors by endogenous glutamate and aspartate enhances the subsequent release of these amino acids. The cellular mechanism may involve Ca2+ influx through presynaptic NMDA receptor channels or liberation of a diffusible neuromodulator linked to the activation of postsynaptic NMDA receptors. (RS)-α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, a selective quisqualate receptor agonist, and kainate, an agonist active at both kainate and quisqualate receptors, selectively depressed the K+-evoked release of aspartate. Conversely, 6-cyano-7-nitroquinoxaline-2,3-dione, an antagonist active at both quisqualate and kainate receptors, selectively enhanced aspartate release. These results suggest that glutamate can negatively modulate the release of aspartate by activating autoreceptors of the quisqualate, and possibly also of the kainate, type. Thus, the activation of excitatory amino acid receptors has both presynaptic and postsynaptic effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1991.tb02063.x
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  • 2
    Electronic Resource
    Electronic Resource
    Arsenic(V) Removal from Aqueous Solutions by Iron(III) Loaded Chelating Resin (2000)
    Springer
    Journal of radioanalytical and nuclear chemistry 246 (2000), S. 597-600 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A study of arsenic adsorption using iron(III) loaded chelating resin as adsorbent is presented. The experiments were carried out in batch mode by using aqueous solutions containing 1000 ppm As, and using an iron(III) loaded iminodiacetate resin (LEWATIT TP 207) with sorption capacity of 168 mg Fe/g resin. The equilibrium time for adsorption was found to be one hour under the experimental conditions used. The influence of pH was studied in the range of 0.8÷8.5. The highest arsenic adsorption was found at pH 1.7. Under these conditions the adsorption capacity for As was approximately 60 mg As/g resin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006713618799
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of the membrane activity on the performance of a catalytic membrane reactor (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 3095-3104 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mathematical model for a catalytic membrane reactor for oxidative coupling of methane (OCM), in which the membrane acts as an oxygen distributor to a bed of catalyst, is presented. From experimental data obtained using several silica membranes impregnated with Li and/or Na, which were prepared by the sol-gel method using alumina supports, the catalytic activity of the membrane was included in the so-called real membrane reactor (RMR) model. Then, the RMR performance was compared with that of the ideal membrane reactor (IMR), whose membrane was supposed to have no activity for the OCM and with experimental data obtained in membrane reactors. Since the membrane activity was implemented in the RMR model, for the first time in the literature, maxima in the hydrocarbon selectivity-methane conversion curves were predicted in agreement with previous experimental trends. Besides, the IMR performance was compared with that of the fixed-bed reactor (FBR), giving the maximum improvement of a membrane reactor over the FBR. Key factors for the future improvement of the performance in this kind of membrane reactor are deduced from these simulations.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690431120
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    Paper (German National Licenses)
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