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  • Artikel  (118)
  • Artikel: DFG Deutsche Nationallizenzen  (118)
  • Chemistry  (118)
  • 1995-1999  (36)
  • 1965-1969  (34)
  • 1960-1964  (46)
  • 1940-1944  (2)
  • 1
    Digitale Medien
    Digitale Medien
    Elastin dehydration through the liquid and the vapor phase: A comparison of osmotic stress models (1996)
    New York : Wiley-Blackwell
    Biopolymers 39 (1996), S. 627-639 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The swelling and viscoelastic behaviors of samples of purified arterial elastin were investigated to develop a model for studying the viscoelastic behavior of elastin. Two osmotic stress models were used: the vapor phase model (VPM), in which the stress on the elastin sample was applied through the vapor phase by equilibrating the sample over a saline solution, and the liquid phase model (LPM), in which the stress was applied through the liquid phase by equilibrating the sample in aqueous solutions of large molecular weight polymers. The elastin in the VPM showed a highly varied viscoelastic response, and was slightly stiffer and had a slightly higher damping coefficient than the elastin in the LPM at equivalent nominal relative humidities. We believe the difference in behavior of the elastin in the two models was due to geometric distortions of the elastin that occur during dehydration in the VPM. In the LPM, the spaces between the elastin fibrils are filled with water, and in the VPM these spaces collapse when the water is removed. Removal of only the interfibrillar water deswelled the tissue and increased its stiffness and damping coefficient.Viscoelastic spectra obtained at different levels of osmotic stress in the LPM were reducible to one master curve, indicating that the dominant effect of dehydration is a nonspecific reduction of molecular mobility. We conclude that the LPM is a better model than the VPM for studying the effects of dehydration on the mechanical behavior of elastin. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    The dynamics of the helix-coil transition in poly-α, L-glutamic acidAn account of this work formed part of a paper delivered at the Fifth International Congress of Biochemistry, Moscow, 1961. (1964)
    New York : Wiley-Blackwell
    Biopolymers 2 (1964), S. 489-500 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Temperature jump measurements employing optical rotation to follow transients show an upper limit of 10μsec. on the half time of the helix-random coil relaxation in poly-α, L-glutamic acid. No relaxations are observed under conditions where the polymer exists in completely helical or completely random coil form. Assuming that the helix-coil transition can be described kinetically as a pure growth process, expressions for the relaxation time are derived for three special cases. A comparison is made between the rate of the helix-coil transition and the rate of imide proton exchange.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1964.360020507
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  • 3
    Digitale Medien
    Digitale Medien
    Low-sulfur proteins from α-keratins. Interrelationships between their amino acid compositions, α-helix contents, and the supercontraction of the parent keratin (1966)
    New York : Wiley-Blackwell
    Biopolymers 4 (1966), S. 905-916 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: S-Carboxymethyl (SCM) kerateine preparations from a range of keratins were fractionated by acid precipitation into low-sulfur (SCMKA) and high-sulfur (SCMKB) fractions. Amiono acid analyses and optical rotatory dispersion measurements on the SCMKA fractions from different keratins indicated that the proportion of α-helical material (30-64%) increased with increasing leucine and glutamic acid contents and decreased with increasing SCM-cysteine and proline contents. It is shown that these variations in α-helix contents are due mainly to differences in the conformations of the principal components of the SCMKA fractions, although there is also a smaller contribution arising from contamination with varying amounts of non helical components. The thiol + disulfide contents for the parent keratins were measured and compared with the SCM -cysteine contents of the solubilized fractions. In general the SCM-cysteine contents of the SCMKA fractions increased with increasing thiol + disulfide content of the parent keratin, but these values were not directly proportional. The extent of total supercontraction in 8M LiBr solution was measured for the parent keratins and shown to bear no significant relationship to their disulfide contents. From the extents of first-stage and total supercontractions the disulfide contents of the contractile structures in the fibers were calculated according to a model described previously and compared with the analytical values for the SCM -cysteine contents of the SCMKA and SCMKB fraction. Data for both fractions were consistent with the model in that they were in each case related to the calculated values by a constant factor. However, because of simplifying assumptions in the model, it was not possible to identity positively one or other of these protein fractions with the contractile elements in the fiber.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.1966.360040807
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  • 4
    Digitale Medien
    Digitale Medien
    Quartz dissolution kinetics from 100-200°C as a function of pH and ionic strength (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 3442-3457 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Of importance to geothermal energy development, oil, gas and mineral recovery, and waste storage is the characterization of the dissolution rate of host reservoir rock as a function of temperature, pressure and liquid-phase composition. As a major constitutive mineral in natural geologic systems, quartz was selected for study. Dissolution experiments were carried out in a continuous-flow, titanium autoclave reactor system at 100-200°C in various chemical environments. Acidification to pH 1.1 using nitric acid showed very little effect on the quartz dissolution rate. The effect of hydroxide ion concentration and ionic strength were evaluated in NaOH, NaOH/NaCl and NaOH/Na2SO4 solutions. The fractional-order dependency of the quartz dissolution rate on hydroxide ion and sodium ion (or ionic strength) concentration was determined in NaOH/NaCl solutions. The results that extend the available range of kinetic data for quartz generally agree with previous work. The observed fractional-order kinetics were qualitatively described using classical adsorption isotherms. No significant variation in the apparent reaction order of the hydroxide ion with increasing temperature could be determined due to the scatter in the data. Quartz dissolution rates were slower by about 40% in NaOH/Na2SO4 solutions than in NaOH/NaCl solutions at sodium concentrations higher than 0.01 molal. The apparent activation energy from 100 to 200°C in NaOH/NaCl solutions up to 0.01 molal hydroxide ion and 0.1 molal sodium ion was estimated to be 72 (±6) kJ/mol.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690421214
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  • 5
    Digitale Medien
    Digitale Medien
    Flow regimes of the three-phase circulating fluidized bed (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 267-271 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Gas-solids circulating fluidized beds have been successfully used in catalytic cracking of heavy oil, coal combustion, and some metallurgical and physical processes (Grace, 1990). Gas-liquid-solids fluidized beds are operated mainly in conventional fluidization regimes without solids circulation or in the transport regime with low solids holdups (less than 5%) (Fan, 1989). A circulating/fast fluidization regime, however, has not been studied. A three-phase circulating fluidized bed has several potential applications in biochemical and chemical processes. Three-phase fluidized-bed bioreactors generally use light and small particles (Berk et al., 1984). Circulating operation can promote solids mixing and increase product throughput per unit bed cross section, while high shear stress can promote biofilm renewal (Pirozzi et al., 1990). In three-phase hydrotreating reactors, solids catalysts lose their activity due to the deposit of metal and coke on the surface. Circulating operation not only regenerates deactivated catalyst continuously using accompanying downcomers but also transfers heat to and from the reactor. This article discusses the flow regimes of the three-phase circulating fluidized bed.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690410209
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  • 6
    Digitale Medien
    Digitale Medien
    Influence of dynamic interfacial properties on droplet breakup in plane hyperbolic flow (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1436-1447 
    Details
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Droplet breakup in laminar flows is important in emulsification processes and polymer blending. The influence of surfactants on droplet deformation and breakup in a plane hyperbolic flow was studied experimentally in an opposed-stream device. As in the case of simple shear flow, the inhomogeneity of the surfactant distribution along the droplet interface has a pronounced effect. Our results are qualitatively consistent with other numerical studies for droplet breakup in an axisymmetric elongational flow. Also a striking similarity is noted with other experimental observations for the deformation and breakup of polymeric drops in a quasi-steady-plane hyperbolic flow. The critical capillary number for droplet breakup in the experiments correlates with the interfacial viscoelasticity, and a reformulation of the numerical framework in terms of interfacial elasticity parameters is suggested for future numerical work including other linear flows.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aic.690430607
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  • 7
    Digitale Medien
    Digitale Medien
    Microbial production of amino acids. I. The synthesis of lysine and threonine by ustilago species (1962)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 4 (1962), S. 23-36 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The ability of a number of Ustilago species, especially Ustilago maydis (DC.) Cda., to produce lysine and threonine was investigated. The organisms were grown in shake flasks or in 10-l. fermentors. Lysine and threonine were found to be excreted into the medium both in the free and bound form. The bound amino acids could be released by acid hydrolysis or by enzymes from autolyzed cells. The optimal conditions for the release by autolysis were, in the case of Ustilago maydis (DC.) Cda., pH 4.3 and 45°C. An enzyme that could liberate lysine from the bound form(s) occurring in the broth was extracted from cells of Ustilago maydis (DC.) Cda. It exhibited an apparent pH optimum near 4.0. The effect of pH and temperature during the growth phase on the yield of lysine and threonine was studied in 10-l. fermentations.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260040105
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  • 8
    Digitale Medien
    Digitale Medien
    Microbial production of amino acids. II. The influence of carbon and nitrogen sources and metal ions on growth of Ustilago maydis (DC.) Cda. and on lysine and threonine production (1962)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 4 (1962), S. 37-52 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The ability of Ustilago maydis (DC.) Cda. to grow and to produce lysine and threonine was investigated in shake flask cultures. Growth and production of lysine and threonine increased markedly when aeration was increased. The optimal ratio of glucose to diammonium phosphate in the medium seemed to be approximately 10:1. Ammonium phosphate, ammonium sulfate, ammonium chloride, ammonium nitrate, sodium nitrate, urea, aspartic acid, glutamic acid, and glycine were readily used as nitrogen sources. Growth and amino acid production was poor on ammonium carbonate, ammonium acetate, ammonium citrate, trimethylamine, and betaine.U. maydis (DC.) Cda. was found to grow on a number of different carbohydrates. Besides D-glucose the organism could utilize D-mannose, D-galactose, D-fructose, L-arabinose, D-xylose, D-ribose, sucrose, maltose, and the polyalcoholes D-sorbitol, D-mannitol, and i-inositol. Pectin, dextrin, and corn starch treated with α-amylase could also be used but not untreated corn starch or lactose, cellobiose, D-sedoheptulose, glycerol, or D-glucosamine. The formation of lysine and threonine was better with disaccharides and hexoses than with pentoses.No specific effects on the formation of lysine and threonine could be observed from changes in the concentration of calcium, sodium, potassium, magnesium, zinc, iron, copper, manganese, cobalt, or molybdenum. The requirement of metal ions for growth is discussed.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260040106
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  • 9
    Digitale Medien
    Digitale Medien
    Untersuchungen von Makroelementen an Rohrleitungen (1966)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 17 (1966), S. 307-315 
    Details
    ISSN: 0947-5117
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Investigations on macroelements on pipelinesExternal corrosion of buried pipelines and tanks is often due to the formation of macroelements. these occur as a result of differentiated aeration, electrolytical composition, formation of surface layers, passivation, or contact between different metals, i.e. where there are local differences in the current/potential curves.The effect of, and results of measurementsfrom, macroelementsare described with the aid of three practical examples: 1long line currents of a pipeline in different geological strata,2aerated elements of protective casings and tanks, and3galvanic formation of cells in soils containing coke.With differentiated aeration, it does not necessarily follow that every compensating current has the effect that the corrosion rate of the less aerated electrode is higher than that of the better aerated electrode. Pit corrosion on aerated elements can only occur if, despite its more positive potential, the better aerated electrode has a lower corrosion rate than the less aerated electrode. This may happen if, because of a change in the PH value, the aerated electrode is strongly polarized or can become passivated with an electron-conductive cover layer.
    Notizen: Die äußere Korrosion unterirdischer Rohrleitungen und Behälter ist oft auf die Ausbildung von Makroelementen zurückzuführen. Makroelemente treten bei unterirdischer Belüftung, elektrolytischer Zusammensetzung, Deckschichtenbildung, Passivierung oder bei Berührungen verschiedener Metalle auf, also kurz bei lokalen Unterschieden bei Strompotentialkurven.Wirkung und Meßergebnisse von Makroelementen werden an drei praktischen Beispielen beschrieben: 1Long line currents einer Fernleitung in unterschiedlichen geologischen Bodenformationen,2Belüftungeselemente von Schutzrohren and Lagerbehältern sowie3galvanische Elementbildung in kokshaltigen Böden.Bei unterschiedlicher Belüftung muß nicht bereits jeder Ausgleichstrom dazu führen, daß die Korrosionsgeschwindigkeit der geringer belüfteten Elektrode die der besser belüfteten überwiegt. Lochfraßkorrosion bei Belüftungselementen ist nur dann möglich, wenn die besser belüftete Elektrode trotz ihres positiveren Potentials eine geringere Korrosionsgeschwindigkeit hat als die geringer belüftete Elektrode. Dies ist möglich, wenn die belüftete Elektrode infolge pH-Wert-Änderung stark polarisiert wird oder sich mit einer elektronenleitenden Deckschicht passivieren kann.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/maco.19660170405
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  • 10
    Digitale Medien
    Digitale Medien
    Kontrollmessungen an kathodisch geschützten RohrleitungenNach einem Vortrag erstattet auf dem 3. Kongreß der Europäischen Föderation Korrosion, Brüssel, Juni 1963. (1964)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 15 (1964), S. 201-212 
    Details
    ISSN: 0947-5117
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Control measurements on cathodically protected pipelinesThe most important control measurement for the cathodic protection of buried pipelines is the measurement of the pipel soil potential. On the strength of experimental and theoretical investigations, it is possible to indicate safe protection potentials at which the corrosion rate becomes practically insignificant. In applying the scientific results of electro-chemistry to cathodic protection in practice, problems may be encountered if phenomena are over-simplified or if local conditions are not sufficiently taken into account.Such practical problems are not so much concerned with measuring instruments and reference electrodes; they are more associated with the measuring methods subsequently described and with the fact that influence factors difficult to ascertain must be taken into account.The cathodic polarisation at the metal surface to be protected is composed of overtensions of a penetration and a diffusion type. In addition, there occurs a resistance polarisation which may be governed, on the one hand, by the ohmic voltage drop between pipe surface and reference electrode and, on the other hand, by poorly conducting coating or insulating layers. The latter usually cause, at the same time, a change in the diffusion type overtension. Since the resistance polarisation does not partake in the reaction kinetics, this influence must be eliminated in measuring the protection potential. Since the different types of polarisation have different type curves, it is possible to ascertain the separate partial reactions in accordance with the normal methods of electro-chemistry. By means of oscillographic recordings of potential/time curves, through calculation or with the aid of suitable measuring bridges, it is possible to eliminate the resistance polarisation or to determine the ohmic voltage drop in the electrolyte.
    Notizen: Die wichtigste Kontrollmessung für den kathodischen Schutz erdverlegter Rohrleitungen ist die Messung des Rohr/Boden-Potentials. An Hand experimenteller und theoretischer Untersuchungen ist es möglich, sichere Schutzpotentiale anzugeben, bei denen die Korrosionsgeschwindigkeit praktisch bedeutungslos wird. Bei der Anwendung wissenschaftlicher Ergebnisse der Elektrochemie auf den kathodischen Schutz in der Praxis können Probleme auftreten, wenn Vorgänge zu stark vereinfacht und örtliche Gegebenheiten nicht genügend berücksichtigt werden.Solche praktischen Probleme liegen weniger bei Meßgeräten und Bezugselektroden, als bei den anschließend beschriebenen Meßverfahren und der Berücksichtigung schwer erfaßbarer Einflußgrößen. Die kathodische Polarisation an der Zu schützenden Metalloberfläche Setzt sich aus einer Durchtritts- und einer Diffusionsüberspannung zusammen. Ferner tritt eine Widerstandspolarisation auf, die einerseits durch den Ohmschen Spannungsabfall zwischen Rohroberfläche und Bezugselektrode, andererseits durch schlecht leitende Deck- oder Isolierschichten gegeben sein kann. Letztere verursachen meist gleichzeitig eine Änderung der Diffusionsüberspannung. Da die Widerstandspolarisation keinen Anteil an der Reaktionskinetik besitzt, muß ihr Einfluß bei der Schutzpotentialmessung eliminiert werden. Auf Grund eines zeitlich unterschiedlichen Verhaltens der Polarisationsarten gelingt die Aufspaltung der einzelnen Teilreaktionen nach den in der Elektrochemie üblichen Verfahren. Durch oszillographische Aufnahme won Potential-Zeitkurven, durch Rechnung oder mit geeigneten Meßbrücken kann die Widerstandspolarisation ausgeschaltet bzw. der Ohmsche Spannungsabfall im Elektrolyten ermittelt werden.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/maco.19640150302
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