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  • 1
    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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  • 2
    ISSN: 1432-0878
    Keywords: Melanotrophs ; Immunogold technique ; Secretory vesicles ; γ3-MSH ; α-MSH ; Endorphins ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The immunogold technique, employing antisera with clear-cut specificities, was used to localise different processing stages of pro-opiomelanocortin (POMC) in rabbit melanotropic cells. While the antiserum against γ 3-MSH labelled all the secretory granules including intrasaccular condensations in the Golgi apparatus, antisera against α-MSH only labelled extra-Golgi secretory vesicles (SV). All extra-Golgi SV were likewise labelled with the three antisera against α-MSH used, despite their different specificities for the desacetylated, N-acetylated or C-amidated forms of the peptide. The antibody against β-endorphin also labelled the extra-Golgi SV, while only some SV were labelled with the antibody against γ-endorphin. These results correlate with biochemical data in favour of mainly — if not exclusively — intragranular processing of POMC. Except for γ3-MSH, the cleavage of which could coincide with Golgi packaging of secretory material, other post-translational modifications of the precursor seem to occur when SV are discharged outside the Golgi area. The cleavage of γ-endorphin appears to be a later step in POMC processing, occurring in some mature SV.
    Type of Medium: Electronic Resource
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  • 3
    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: Electrochemical investigations into the corrosion behaviour of electrolytically and chemically deposited metallic coatings in chloride containing solutionsBehaviour of chemically deposited coatings (Nip-alloy, NiB-alloys), electrolytically deposited coatings (Ni, Zn, Cd, hard Cr and Cu) and  -  for the purpose of comparison  -  CrNi steel 18 8 in NaCl solutions (0.6, 2.91, 14.16 and 24.18 weight %) with NaCl concentration, oxygen concentration and temperature as variables. In aerated systems the oxygen concentration is rate controlling; in this context, characteristic differences are found, depending from the noble character of the particular metal. The temperature has little bearing on the corrosion current.
    Notes: Verhalten von stromlos abgeschiedenen Überzügen (Nip-Leg., NiB-Leg.), elektrolytisch abgeschiedenen Überzügen (Ni, Zn, Cd, Hartchrom, Cu) und  -  als Vergleichswerkstoff  -  CrNi-Stahl 18 8 in NaCl-Lösungen (06, 2,91, 14,16 und 24,18 Gew.%) unter Berücksichtigung von NaC1-Konzentration, Sauerstoffkonzentration und Temperatur als Variablen. In belüfteten systemen ist die Sauerstoffkonzentration geschwindigkeitsbestimmend, wobei sich charakteristische Unterschiede je nach dem edlen Charakter des Metalls ergeben. Die Temperatur beeinflußt den Korrosionsstrom nur wenig.
    Additional Material: 10 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 24 (1973), S. 118-122 
    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: The electrochemical behaviour of pure lead in hot sulfuric acid at high concentrationsThe corrosion rate of pure lead in 70% deaerated sulfuric acid can be calculated for the temperature range between 21 and 165 °C using one only equation. The possibility of an extension of this equation by a concentration dependent term is made feasible by the finding, that a logarithmic dependence exists between corrosion rate and acid concentration in the concentration rate 10-80% at 80 °C. In connection with the interpretation of the current density potential curves of pure lead in hot concentrated sulfuric acid the authors discuss the possibility of lead sulfide formation.
    Notes: Die Korrosionsgeschwindigkeit von Feinblei in 70proz. entlüfteter Schwefelsäure 1äßt sich für den Temperaturbereich von 25-165 °C mittels einer Bestimmungsgleichung berechnen. Die Möglichkeit der Erweiterung dieser Gleichung durch einen konzentrationsabhängigen Term wird durch das Auffinden einer logarithmischen Abhängigkeit der Korrosionsgeschwindigkeit von der Säurekonzentration im Konzentrationsbereich von 10-80 Gew.-% und einer Temperatur von 80 °C wahrscheinlich gemacht.Bei der Interpretation der Stromspannungskurven von Feinblei in heißen konzentrierten Schwefelsäuren wird die Bildung von Bleisulfid diskutiert.
    Additional Material: 5 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 28 (1977), S. I 
    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
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 29 (1978), S. 98-100 
    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: Investigations into the Corrosion Mechanism of Mild Steel in Oxygen-Free Carbon Dioxide Solutions. Part II. Kinetic of Iron DissolutionMeasuring the potential dependence of the anodic iron dissolution at mild steel in O2-free CO2-containing 0,5 M sodium sulfate solutions at temperatures between 25 and 75 °C an anodic Tafel-slope of ba = 40 ± 1 mV was found. This means that the active iron dissolution follows the uncatalyzed Bockris-mechanism. The corrosion rates at the free corrosion potential were measured in dependence of temperature and CO2 concentration by extrapolation of anodic Tafellines and by polarisation resistance measurements. From these results the activation energy of the iron dissolution was calculated to be 50 to 100 kJ/mol depending on pH. Based on all experimental results a complete corrosion mechanism is formulated.
    Notes: Durch Ermittlung der Potentialabhängigkeit der anodischen Eisenauflösungsgeschwindigkeit an unlegiertem Stahl in sauerstofffreien kohlendioxidhaltigen 0,5 M Natriumsulfatlösungen wurde bei Temperaturen von 25 bis 75°C eine Steigung der anodischen Tafelgeraden von ba = 40 ± 1 mV gemessen. Hieraus folgt, daß die aktive Eisenauflösung in diesem Temperaturbereich nach dem unkatalysierten Bockris-Mechanismus verläuft. Durch Extrapolation anodischer Tafelgeraden und durch Polarisationswiderstandsmessungen wurden die Korrosionsgeschwindigkeiten am Ruhepotential in Abhängigkeit von der Temperatur und der Kohlendioxidkonzentration ermittelt. Aus diesen Werten konnte die Aktivierungsenergie der Eisenauflösung berechnet werden. Sie liegt je nach pH-Wert der Lösung zwischen 50 und 100 kJ/mol. Auf Basis der bisherigen Untersuchungen wurde ein vollständiger Korrosionsmechanismus formuliert.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 29 (1978), S. 237-245 
    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 of unalloyed and low alloyed steels in carbonic acid solutionsIn long period experiments unalloyed steels were found to corrode in O2-free CO2-saturated 0,5 M sodium sulfate solutions at 25° C with flow independent corrosion rates of 0,05-0,1 mm/a. Cold-work at unalloyed steels as well as higher contents of phosphorus, copper and chromium in unalloyed and low alloyed steels increased the corrosion rate to 0,2 to 1,4 mm/a. In O2-free CO2-saturated distilled water unalloyed steel showed a decreased resistance affording corrosion rates of 0,4 mm/a. Traces of oxygen as introduced by CO2 containing 100 ppm O2 increased the corrosion rate only above pH 4,2. All investigated unalloyed and low alloyed steels showed pitting corrosion after long induction periods. The shortest induction periods were observed in O2-free CO2-saturated distilled water. Sulfate ions and traces of oxygen seem to inhibit pitting corrosion.
    Notes: In Langzeitversuchen wurden für unlegierte Stähle in O2-freier, CO2-gesättigter 0,5 M Natriumsulfatlösung bei 25 °C strömungsunabhängige Abtragsraten von 0,05 bis 0,1 mm/a gemessen. Kaltverformung bei unlegiertem Stahl sowie höhere Gehalte an Phosphor, Kupfer und Chrom in un- und niedriglegierten Stählen steigerten die Korrosionsgeschwindigkeit auf 0,2 bis 1,4 mm/a. In O2-freiem, CO2-gesättigtem destilliertem Wasser wies unlegierter Stahl mit Korrosionsraten von 0,4 mm/a eine geringere Beständigkeit auf. Sauerstoffspuren, wie sie durch 100 ppm O2 enthaltendes CO2 eingetragen wurden, beschleunigten die Korrosion erst oberhalb pH 4,2. Alle untersuchten un- und niedriglegierten Stähle zeigten nach längeren Induktionszeiten z. Tl. erhebliche Lochkorrosion. Die kürzesten Induktionszeiten wurden in O2-freiem, CO2-gesättigtem destilliertem Wasser beobachtet. Sulfationen und Sauerstoffspuren scheinen die Lochkorrosion zu verzögern.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 48 (1997), S. 631-639 
    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: AC impedance investigations on the performance of inhibitors and surfactants in CO2 corrosion of steel under natural gas production conditionsInhibition mechanisms of CO2, corrosion of low alloy carbon steel (38 Mn 6) were studied under production conditions of sweet natural gas (1 M NaCl + 0.1 M CaCl2; 1 and 5 bar CO2; 80°C) in the presence of surface active compounds (inhibitors, surfactants) with AC impedance spectrometry. Based on a pore model an equivalent circuit was developed which explains the action mechanisms of the substances tested. Fatty amines and imidazolines inhibit the interface reaction at the bottom of pores in the corrosion product scale due to adsorption. Nonionic surfactants can impair the effectivity of N-containing inhibitors. 1-Octyne-3-ol acts through formation of polymer films and reduces the porosity of the scale. All substances under investigation influence the morphology of the scale and the kinetic of its formation.
    Notes: Inhibitionsmechanismen der CO2 Korrosion von niedriglegiertem C-Stahl (38 Mn 6) warden unter den Bedingungen der Förderung süßer Erdgase (1 M NaCl + 0,1 M CaCl2 I und 5 bar CO2 80°C) in Gegenwart von grenzflächenaktiven Stoffen (Inhibitoren, Tenside) mit Hilfe der elektrochemischen Impedanzspektrometrie studiert. Auf Basis eines Porenmodells wurde ein Ersatzschaltbild entwickelt, mit welchem die Mechanismen der untersuchten Werkstoffe beschrieben werden können. Fettamine und Imidazoline hemmen die Phasengrenzreaktion am Grunde von Deckschichtporen durch Adsorption. Nichtionische Tenside können die Wirksamkeit der N-haltigen Inhibitoren beeinträchtigen. 1-Octin-3-ol wirkt durch Polymerisatfilmbildung und Reduzierung der Deckschichtporosität. Alle Wirkstoffe beeinflussen die Morphologie der Deckschicht und ihre Bildungskinetik.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 48 (1997), S. 586-601 
    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: Hochentwickelte elektrochemische Methoden zur Untersuchung und Überwachung von mikrobiologisch beeinflußter KorrosionAufgrund der elektrochemischen Natur der mikrobiologisch beeinflußten Korrosion (MIC) eignen sich elektrochemische Methoden sehr gut zum Studium der Reaktionen an der Phasengrenze Metall/Biofilm, zur Untersuchung von Reaktionsmechanismen und zur Überwachung des Beginns und Fortschreitens von MIC. Der vorliegende Übersichtsartikel diskutiert verschiedene elektrochemische Methoden-Messung des Korrosionspotentials, Redoxpotentials, Polarisationswiderstandes, galvanischer Elementströme; Großsignal-Polarisationstechniken, Zufalls-Potentialpulsmethode, elektrochemische Impedanzspektrometrie, elektrochemische Relaxationsmethoden (programmierte Pulsrelaxation, sinusoidale Wechselstromrelaxation), elektrochemische Rauschanalyse, rasternde Vibrationselektrodentechniken (Kelvin Sonde, vibrierende Mikrobezugselektrode, elektrochemische Sensoren)unter Berücksichtigung ihrer Anwendungsbreite und Eignung für Aufgaben der Untersuchung und Überwachung, von MIC.
    Notes: Due to the electrochemical nature of MIC electrochemical methods are useful tools to study reactions at the metal/biofilm interface, investigate MIC mechanisms and monitor the onset of MIC and its propagation. The paper discusses various electrochemical methods - measurement of corrosion potential, redox potential, polarization resistance, galvanic currents, large signal polarization techniques, random potential pulse method, electrochemical impedance spectrometry, electrochemical relaxation methods (programmed pulse relaxation, sinusoidal ac relaxation), electrochemical noise analysis, scanning vibrating electrode techniques (Kelvin probe, vibrating microreference electrode, electrochemical sensors)-;with respect to their applicability and merits for MIC investigations and monitoring.
    Additional Material: 28 Ill.
    Type of Medium: Electronic Resource
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  • 10
    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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