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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 35 (1984), S. 99-106 
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Acid inhibitors. II. Influence of quarternary ammonium salts on the hydrogen absorption of mild steel in H2S-free and H2S-saturated hydrochloric acidThe influence of organic ammonium salts (pyridine hydrochloride and its derivates, trialkylbenzylammonium halides, pyridines, quinolinium and isoquinolinium compounds quaternarized with benzyl halides and substituted benzyl chlorides) on the hydrogen absorption of mild steel treated with H2S-free and H2S-saturated 16% hydrochloric acid at 25 °C was studied using electrochemically controlled hydrogen permeation measurements. Investigations on structure-efficiency correlations revealed that the inhibitors can influence the kinetics of the hydrogen absorption and the rate of metal dissolution with significantly different efficiency. Describing the efficiency profil of acid inhibitors it is therefore necessary to test inhibitors in both respects. This is valid especially in the presence of H2S which can change the efficiency of inhibitors fundamentally.Besides by structural and electronic variations in the organic molecule the efficiency of the inhibitors tested was influenced by the type of anion (e.g. bromide, iodide). With benzylquinolinium chloride the best results were found in both H2S-free and H2S-saturated acid.
    Notes: Mit Hilfe elektrochemisch kontrollierter Wasserstoffpermeationsmessungen wurde der Einfluß organischer Ammoniumsalze (Pyridinhydrochlorid und Derivate, Trialkylbenzylammoniumhalogenide, mit Benzylhalogeniden und substituierten Benzylchloriden quaternärisierte Pyridine, Chinoline und Isochinoline) auf die Wasserstoffabsorption von unlegiertem Stahl beim Behandeln mit H2S-freier und H2S-gesättigter 16%iger Salzsäure bei 25 °C studiert. Untersuchungen zu Struktur-Wirkungsbeziehungen zeigten, daß die betrachteten Inhibitoren die Kinetik der Wasserstoffabsorption im Metall und die Geschwindigkeit der Metallauflösung durchaus unterschiedlich beeinflussen können. Daher müssen zur Beschreibung des Wirkprofils von Säureinhibitoren stets beide Einflußbereiche untersucht werden. Dies gilt vor allem in Anwesenheit von H2S, welches die Eigenschaften von Inhibitoren grundlegend verändern kann.Neben strukturellen und elektronischen Veränderungen im organischen Teil des Inhibitormoleküls zeigten auch Variationen des Anions (z. B. Bromid, Iodid) einen deutlichen Einfluß auf die Inhibitionswirkung. Mit Benzylchinoliniumchlorid wurden die besten Resultate sowohl in H2S-freier Säure als auch in Anwesenheit von H2S erhalten.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 35 (1984), S. 107-110 
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Acid inhibitors. II. Influence of quarternary ammonium salts on the hydrogen absorption of mild steel in H2S-free and H2S-saturated formic acidThe influence of quaternary ammonium compounds (benzylpyridinium chloride, benzylquinolinium halides, p-dodecylbenzylquinolinium chloride, benzylisoquinolinium chloride, tri-n-butylbenzylammonium halides, benzyldabcolinium chloride) on the rate of metal dissolution and absorption of corrosion hydrogen in the metal was studied at mild steel in chloride containing 10% formic acid at 25 °C in the presence and absence of H2S. Generally the same effects were observed like in the system steel/hydrochloric acid. Depending on the kind of inhibitor the presence of H2S increased or decreased the efficiency of inhibitors to block the H-absorption. Regardless of the presence of H2S p-dodecylbenzylquinolinium chloride and benzylquinolinium iodide exhibited the best efficiencies in decreasing the rate of metal dissolution and inhibiting the H-absorption in the metal.
    Notes: Es wurde der Einfluß quartärer Ammoniumverbindungen (Benzylpyridiniumchlorid, Benzylchinoliniumhalogenide, p-Dodecylbenzylchinoliniumchlorid, Benzylisochinoliniumchlorid, Tri-n-butylbenzylammoniumhalogenide, Benzyldabcoliniumchlorid) auf das Abtragsverhalten und die Absorption von Korrosionswasserstoff im Metall beim Behandeln von unlegiertem Stahl mit chloridhaltiger 10%iger Ameisensäure bei 25 °C in Anwesenheit und Abwesenheit von H2S studiert. Grundsätzlich wurden ähnliche Effekte wie im System Stahl/ Salzsäure gefunden. H2S-Anwesenheit wirkte sich je nach Inhibitorsubstanz günstig oder ungünstig auf die Kinetik der H-Absorption aus. p-Dodecylbenzylchinoliniumchlorid und Benzylchinoliniumchlorid zeigten unabhängig von der H2S-Anwesenheit die besten Hemmwerte sowohl bei der Metallauflösung als such bei der Absorption von Korrosionswasserstoff.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 35 (1984), S. 556-565 
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Corrosion reactions between elemental sulphur and plain carbon steel in aqueous mediaPlain carbon steels are rather severely attacked by elemental sulphur at room temperature in the presence of aqueous media. The corrosion occurs preferentially at the places where the two solid substances iron and sulphur are in contact with each other and results in shallow pit formation. At the same time the pH is also decreased slightly and small amounts of H2S and sulphate ions are formed. Neutral salts stimulate the corrosion process whereas phosphates inhibit it and the alkaline media such as Na2CO3 and ethylamine with pH 〉 12 prevent it completely. The latter can be made use of for corrosion protection. At high salt concentrations (c 〉 1 mol/l) the corrosion rate, however, decreases with increasing salt concentration. The corrosion rate may increase with increasing flow velocity of the medium, but the corrosion takes place uniformly.The results of electrochemical investigations show that the reduction of sulphur occurs at the corrosion product FeS and is the rate controlling step. No sulphur reduction is observed on platinum electrodes when no FeS is present. It is assumed that the starting reaction to initiate corrosion in the system Fe/S/H2O is a slight disproportionation of S to H2SO4 resulting in the formation of FeS.
    Notes: Unlegierter Stahl wird durch elementaren Schwefel in Gegenwart wäßriger Medien bei Raumtemperatur verhältnismäßig stark angegriffen. Die Korrosion erfolgt bevorzugt an den Berührungsstellen der Feststoffe Fe und S unter Muldenbildung. Gleichzeitig erfolgen eine geringe pH-Absenkung sowie eine geringfügige Bildung von H2S und Sulfat-Ionen. Der Vorgang wird durch Neutralsalze sehr stark stimuliert, durch Phosphate inhibiert und durch alkalische Medien, wie z. B. Na2CO3 und Ethylamin mit pH 〉 12, völlig unterbunden. Dies kann zum Korrosionsschutz genutzt werden. Mit zunehmender Salzkonzentration (c 〉 1 mol/l) nehmen die Abtragungsraten wieder ab. Durch zunehmende Strömungsgeschwindigkeit können die Abtragungsraten zunehmen, wobei aber nur gleichförmiger Flächenangriff auftritt.Elektrochemische Untersuchungen zeigen, daß die Reduktion des Schwefels am Korrosionsprodukt FeS stattfindet und für die Korrosion geschwindigkeitsbestimmend ist. An Pt-Kathoden wird bei Abwesenheit von FeS keine Schwefelreduktion beobachtet. Als Startreaktion für die Korrosion im System Fe/S/H2O wird eine geringe Disproportionierung des S zu H2SO4 angenommen, wobei FeS entsteht.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0878
    Keywords: Melanotrophs ; Immuno-gold technique ; Secretory vesicles ; γ 3-MSH ; α-MSH ; Acetylation ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Melanotrophic cells of the pars intermedia of the rabbit were studied at the electron-microscopic level by means of the immuno-gold technique with the use of antisera against γ 3-MSH and α-MSH. Both antibodies labelled all secretory vesicles stored in the peripheral cytoplasm, but secretory vesicles and intrasaccular condensations in the Golgi area reacting for γ 3-MSH were not labelled with the antibody against α-MSH. Since this antibody appears to recognise only the acetylated form of α-MSH, the present observations suggest that acetylation occurs at a stage subsequent to the Golgi packaging, during maturation of the secretory vesicles. Thus, the morphological evidence supports biochemical data in favour of intragranular processing of opiomelanocortin in melanotrophic cells.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-0878
    Keywords: Pars intermedia (mouse) ; Fine structure ; Morphometry Sodium Dopaminergic control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Quantified ultrastructural observations of the pars intermedia (PI) of the murine hypophysis enable evaluation and kinetic study of relatively fine secretory changes in the gland. Changes in volume of rER and newly formed dense secretory granules (Golgi granules) appear to best translate functional variations in the PI, as shown by the morphological effects of drugs affecting the dopaminergic control of the gland. Our morphometric results show that the PI is stimulated, but only briefly (no longer than 8–12 days), by both salt-loading and Na deprivation. However, the PI displays different secretory patterns in salt-loaded and Na-deprived mice; moreover, bromocriptine, which abolishes PI stimulation in Na-deprived mice, has only a slight inhibitory effect in salt-treated animals. Thus, it appears that the stimulation of the PI under both experimental conditions is triggered by different mechanisms. These results underline the plurifactorial control of the PI and show that the gland may have complex effects on hydromineral regulation.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-0878
    Keywords: Pars intermedia ; Oxytocin ; Dopamine ; Serotonin ; Immunocytochemistry ; Rabbit, hare
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The pars intermedia of the pituitary in the rabbit and hare is abundantly innervated by axons reacting selectively with antibodies against oxytocin. These axons contain dense secretory vesicles about 140 nm in diameter, i.e., smaller than those in the neurosecretory axons of the neural lobe. No fiber elements staining for other peptides (vasopressin, somatostatin, substance P) were observed in the pars intermedia, except rare leu-enkephalin axons restricted to the rostral zone of the gland. Dopaminergic innervation appears to be completely absent from the intermediate lobe. This was shown by the lack of reaction with an antibody against tyrosine-hydroxylase, which did reveal a well-developed tubero-infundibular system of nerve fibers. Axons reacting with an antibody against serotonin were irregularly distributed in the pars intermedia. In the absence of dopaminergic axons, the extensive oxytocin-like innervation may play a major role in regulating the melanotrophic cell activity in the Leporidae.
    Type of Medium: Electronic Resource
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