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  • 1980-1984  (3)
  • Compensation point (CO2)  (1)
  • F1-ATPase  (1)
  • Polymer and Materials Science  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Changes in photosynthetic capacity, carboxylation efficiency, and CO2 compensation point associated with midday stomatal closure and midday depression of net CO2 exchange of leaves of Quercus suber (1984)
    Springer
    Planta 162 (1984), S. 193-203 
    Details
    ISSN: 1432-2048
    Keywords: Carboxylation efficiency ; Compensation point (CO2) ; Photosynthesis (temperature, humidity) ; Quercus ; Sclerophyll
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The carbon-dioxide response of photosynthesis of leaves of Quercus suber, a sclerophyllous species of the European Mediterranean region, was studied as a function of time of day at the end of the summer dry season in the natural habitat. To examine the response experimentally, a “standard” time course for temperature and humidity, which resembled natural conditions, was imposed on the leaves, and the CO2 pressure external to the leaves on subsequent days was varied. The particular temperature and humidity conditions chosen were those which elicited a strong stomatal closure at midday and the simultaneous depression of net CO2 uptake. Midday depression of CO2 uptake is the result of i) a decrease in CO2-saturated photosynthetic capacity after light saturation is reached in the early morning, ii) a decrease in the initial slope of the CO2 response curve (carboxylation efficiency), and iii) a substantial increase in the CO2 compensation point caused by an increase in leaf temperature and a decrease in humidity. As a consequence of the changes in photosynthesis, the internal leaf CO2 pressure remained essentially constant despite stomatal closure. The effects on capacity, slope, and compensation point were reversed by lowering the temperature and increasing the humidity in the afternoon. Constant internal CO2 may aid in minimizing photoinhibition during stomatal closure at midday. The results are discussed in terms of possible temperature, humidity, and hormonal effects on photosynthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397440
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  • 2
    Electronic Resource
    Electronic Resource
    Interaction of high-affinity nucleotide binding sites in mitochondrial ATP synthesis and hydrolysis (1982)
    Springer
    Journal of bioenergetics and biomembranes 14 (1982), S. 479-498 
    Details
    ISSN: 1573-6881
    Keywords: Oxidative phosphorylation ; F1-ATPase ; nucleotide binding sites ; cooperativity ; nucleotide analogs ; fluorescence ; mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The present study contributes to the problem of the dynamic structure of mitochondrial F1-ATPase and the functional interrelation of so-called tight nucleotide binding sites. Nucleotide analogs are used as a tool to differentiate two distinct functional states of the membrane-bound enzyme, proposed to reflect corresponding conformational states; they reveal F1-ATPase as a “dual-state” enzyme: ATP-synthetase, and ATP-hydrolase. The analogs used are 3′-naphthoyl esters of AD(T)P, and 2′(3′)-O-trinitrophenyl ethers of AD(T)P. Both types of analogs act inversely to each other with respect to their relative effects on oxidative phosphorylation and on ATPase in submitochondrial vesicles. The respective ratios ofK i versus both processes are 250/1 compared to 1/170. It is also shown that in the presence of the inhibitory 3′-esters oxidative phosphorylation deviates from linear kinetics and that these inhibitors induce a lag time of oxidative phosphorylation depending on the initial pattern of nucleotides available to energized submitochondrial vesicles. The duration of the lag time coincides with the time course of displacement of the analog from a tight binding site. The conclusions of the study are: (a) the catalytic sites of F1-ATP-synthetase are not operating independently from each other; they rather interact in a cooperative manner; (b) F1-ATPase as a “dual-state” enzyme exhibits highly selective responses to tight binding of nucleotides or analogs in its “energized” (membrane-bound) state versus its “nonenergized” state, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00743073
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  • 3
    Electronic Resource
    Electronic Resource
    Das Verhalten rostfreier Stahlgußlegierungen unter gleichzeitiger mechanischer und korrosiver Belastung (1980)
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 11 (1980), S. 244-258 
    Details
    ISSN: 0933-5137
    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: Behaviour of stainless cast alloys under combined mechanical and corrosive attackIn media with 3000 mg B/1 (as boric acid, H3BO3) and varying chloride contents down to 1 mg Cl-/1 13%-Cr-steels show pitting. Under constant load cracks appear simultaneously. As can be expected, 17%-Cr-steels are more resistant and duplex ferritic austenitic steels exhibit no corrosion cracking in 3% NaCl-solution even after 10 000 hrs. Generally, corrosion resistance improves with increasing contents of ferrite forming elements. Corrosion cracks are interpreted in termes of anodic stress corrosion cracking. Notch impact bending tests with hydrogen charged specimens show that deformability is reduced.
    Notes: 13%-Cr-Stähle zeigen in Lösungen mit 3000 mg B/1 (als Borsäure, H3BO3) und unterschiedlichen Chloridgehalten Lochkorrosion bis herab zu Konzentrationen von 1 mg Cl-/1. Bei mechanischer Zugbeanspruchung treten gleichzeitig Risse auf. 17%-Cr-Stähle sind erwartungsgemäß beständiger und ferritisch-austenitische Stähle zeigen in 3% NaCl-Lösung auch im 10 000 h-Versuch keine Korrosionsrisse. Generell steigt die Beständigkeit mit zunehmendem Anteil an ferritbildenden Elementen. Die Korrosionsrisse werden als anodische Spannungsrißkorrosion interpretiert. Kerbschlagbiegeversuche mit wasserstoffbeladenen Proben ergeben eine Abnahme des Verformungsvermögens.
    Additional Material: 21 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mawe.19800110707
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