Catalysis of thermal exchange reactions between carboxyl groups and14CO2

1989 ◽  
Vol 135 (2) ◽  
pp. 125-129
Author(s):  
J. Szammer ◽  
E. Simon-Trompler ◽  
L. Ötvös
Keyword(s):  
Carboxyl Groups ◽  
Exchange Reactions ◽  
Thermal Exchange

RECOIL-ACTIVATED AND THERMAL EXCHANGE REACTIONS BETWEEN SULFUR-35 AND CARBON DISULFIDE

1948 ◽  
Vol 70 (4) ◽  
pp. 1670-1670 ◽  
Author(s):  
Raymond R. Edwards ◽  
Frances B. Nesbett ◽  
A. K. Solomon
Keyword(s):  
Carbon Disulfide ◽  
Exchange Reactions ◽  
Thermal Exchange

scholarly journals Exchange reactions between deuterium and hydrogen halides. I. Hydrogen chloride

1939 ◽  
Vol 173 (955) ◽  
pp. 503-530 ◽  
Keyword(s):  
Hydrogen Chloride ◽  
Theoretical Calculations ◽  
Bimolecular Reaction ◽  
Activation Energies ◽  
State Theory ◽  
Thermal Method ◽  
Exchange Reactions ◽  
Elementary Reactions ◽  
Thermal Exchange ◽  
Type D

In the majority of gaseous exchange reactions, deuterium atoms, produced photochemically or by an electric discharge, have been employed to initiate the reaction. Only the thermal method offers some prospect of detecting exchange reactions of the type D 2 + HA→DA + HD. At high temperatures in addition atomic reactions will occur initiated by thermally dissociated atoms which, although present in very low concentration, react with very much smaller activation energies. Thus thermal exchange reactions can be brought about by two different mechanisms, their relative velocities being mainly dependent on the activation energies of the elementary reactions involved. Using activation energies derived from band spectroscopic data, Eyring and his collaborators attempted to predict the mechanism for several reactions where such alternative mechanisms were possible (Eyring 1931). Thus in the case of the exchange reaction of hydrogen and deuterium the method was successful in eliminating the molecular and predicting the atomic reaction, in agreement with experiment. The reaction of deuterium and hydrogen chloride offers another possibility of testing such calculations. Previous work indicated the existence of a bimolecular reaction, and it seemed, probable that at higher temperatures the atomic mechanism would intrude (Gross and Steiner 1936). It seemed desirable to investigate whether this reaction really proceeded in both ways and whether the quantitative aspects of this more complicated behaviour could be determined. The reactions have an additional interest, in that the transition state theory can be applied to calculate their rate, since they are sufficiently simple to permit us to derive the necessary data (Wheeler, Topley and Eyring 1936). Experiments were performed with deuterium and hydrogen chloride mixtures, as well as with hydrogen and deuterium chloride. In addition the ortho-para-hydrogen conversion catalysed by hydrogen chloride has been studied. The bimolecular reaction was observed, but an additional atomic chain mechanism was found to take part. The results obtained lead to a consistent mechanism from which the rates of the elementary reactions can be derived. These are then compared with the theoretical calculations.

Influence of Calcium Ions on the Plant Cell Surface: Membrane Fusions and Conformational Changes

1974 ◽  
Vol 32 ◽  
pp. 154-155
Author(s):  
D. James Morré ◽  
Charles E. Bracker ◽  
William J. VanDerWoude
Keyword(s):  
Cell Wall ◽  
Cell Surface ◽  
Conformational Changes ◽  
Calcium Ions ◽  
Surface Membrane ◽  
Carboxyl Groups ◽  
Cross Linking ◽  
Ultrastructural Evidence ◽  
Glycine Max L ◽  
Wall Extensibility

Calcium ions in the concentration range 5-100 mM inhibit auxin-induced cell elongation and wall extensibility of plant stems. Inhibition of wall extensibility requires that the tissue be living; growth inhibition cannot be explained on the basis of cross-linking of carboxyl groups of cell wall uronides by calcium ions. In this study, ultrastructural evidence was sought for an interaction of calcium ions with some component other than the wall at the cell surface of soybean (Glycine max (L.) Merr.) hypocotyls.

Exchange reactions and electrolytic dissociation

1948 ◽  
Vol 45 ◽  
pp. 147-149 ◽  
Author(s):  
C. C. Evans ◽  
S. Sugden
Keyword(s):  
Exchange Reactions ◽  
Electrolytic Dissociation

Modeling of photosynthesis light curves by linear splines

2019 ◽  
pp. 20-29
Author(s):  
Alexander S. Lelekov ◽  
Rudolf P. Trenkenshu
Keyword(s):  
Experimental Data ◽  
Chlorophyll A ◽  
Skeletonema Costatum ◽  
Light Flux ◽  
Photosynthesis Rate ◽  
Light Curves ◽  
External Irradiation ◽  
Exchange Reactions ◽  
Cell Adaptation ◽  
Linear Splines

The paper presents an example of the linear splines use to describe the photosynthesis light curves for microalgae culture. The main mathematical models of the relationship between photosynthesis rate and light are listed. Based on the previously formulated basic principles of modeling microalgae photobiosynthesis, a mathematical model is proposed that describes the dependence of the assimilation number of chlorophyll a on the value of the light flux by linear splines. The advantage of the proposed approach is a clear definition of the point of change of the limiting factor. It is shown that light-limited photosynthesis rate is determined not only by external irradiation, but also by the concentration of chlorophyll a. The light-saturated rate depends on the amount of a key enzyme complex, which limits the rate of energy exchange reactions in the cell. Verification of the proposed model on the example of the diatom microalgae Skeletonema costatum was carried out. It is shown that the higher the degree of cell adaptation to high irradiation, the better the photosynthesis curve is described by linear splines. If S. costatum cells are adapted to low irradiation, deviations of experimental data from the idealized broken line are observed, which are caused by changes in the pigment composition. When the experimental data are normalized, the cell adaptation factor is reduced, all points are described by a single broken line, which indicates the universality of the proposed approach.

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