Catalytic oxidation of n-propane and methyl alcohol over nickel(II) oxide

1981 ◽  
Vol 59 (5) ◽  
pp. 865-869 ◽  
Author(s):  
I. M. Hoodless ◽  
R. A. Ross ◽  
R. Swaminathan

The catalytic oxidation of propane over nickel(II) oxide has been studied in the temperature range 280 to 490 °C. Complete oxidation to carbon dioxide and water occurred. Fractional rate order dependencies were obtained for propane and oxygen and the reaction was inhibited by water vapour but not by carbon dioxide. It is suggested that the interaction of the adsorbed hydrocarbon with the adsorbed oxygen species, O−, is the rate-limiting step in the reaction at the lower temperature.Preliminary measurements of the oxidation of propane–methanol mixtures indicated that the alcohol supressed carbon dioxide formation. Conductivity studies have shown that, in these mixtures, methanol strongly interacts with the catalyst resulting in surface reduction.

Author(s):  
Ayokanmi Ore ◽  
Ebenezer Tunde Olayinka

Herbicides are substances used to control unwanted plants-weeds. They can be classified into several classes by mechanism of action. This review describes the members of aryloxyphenoxypropionate herbicides, their pharmacokinetic properties, metabolism and their mechanism of phytotoxicity in target weeds as well as in non-target organisms. Two major toxicity mechanisms are described. The first is by inhibition of lipid synthesis. This is achieved by inhibiting the rate limiting step of lipid biosynthesis catalyzed by acetyl CoA carboxylase. The second mechanism is by induction of oxidative stress. This is achieved by generation of reactive oxygen species which in excess can cause oxidative damage to macromolecules and cellular structures especially the membrane lipids. Loss of vital membrane lipids alters the fluidity of membrane, loss of cellular contents and eventually cell death and death of the entire plant.


2021 ◽  
Vol 12 ◽  
Author(s):  
Dalong Zhang ◽  
Qingjie Du ◽  
Po Sun ◽  
Jie Lou ◽  
Xiaotian Li ◽  
...  

The atmospheric vapour pressure deficit (VPD) has been demonstrated to be a significant environmental factor inducing plant water stress and affecting plant photosynthetic productivity. Despite this, the rate-limiting step for photosynthesis under varying VPD is still unclear. In the present study, tomato plants were cultivated under two contrasting VPD levels: high VPD (3–5 kPa) and low VPD (0.5–1.5 kPa). The effect of long-term acclimation on the short-term rapid VPD response was examined across VPD ranging from 0.5 to 4.5 kPa. Quantitative photosynthetic limitation analysis across the VPD range was performed by combining gas exchange and chlorophyll fluorescence. The potential role of abscisic acid (ABA) in mediating photosynthetic carbon dioxide (CO2) uptake across a series of VPD was evaluated by physiological and transcriptomic analyses. The rate-limiting step for photosynthetic CO2 utilisation varied with VPD elevation in tomato plants. Under low VPD conditions, stomatal and mesophyll conductance was sufficiently high for CO2 transport. With VPD elevation, plant water stress was gradually pronounced and triggered rapid ABA biosynthesis. The contribution of stomatal and mesophyll limitation to photosynthesis gradually increased with an increase in the VPD. Consequently, the low CO2 availability inside chloroplasts substantially constrained photosynthesis under high VPD conditions. The foliar ABA content was negatively correlated with stomatal and mesophyll conductance for CO2 diffusion. Transcriptomic and physiological analyses revealed that ABA was potentially involved in mediating water transport and photosynthetic CO2 uptake in response to VPD variation. The present study provided new insights into the underlying mechanism of photosynthetic depression under high VPD stress.


2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Stefan Ringe ◽  
Carlos G. Morales-Guio ◽  
Leanne D. Chen ◽  
Meredith Fields ◽  
Thomas F. Jaramillo ◽  
...  

AbstractElectrochemical CO$$_{2}$$2 reduction is a potential route to the sustainable production of valuable fuels and chemicals. Here, we perform CO$$_{2}$$2 reduction experiments on Gold at neutral to acidic pH values to elucidate the long-standing controversy surrounding the rate-limiting step. We find the CO production rate to be invariant with pH on a Standard Hydrogen Electrode scale and conclude that it is limited by the CO$$_{2}$$2 adsorption step. We present a new multi-scale modeling scheme that integrates ab initio reaction kinetics with mass transport simulations, explicitly considering the charged electric double layer. The model reproduces the experimental CO polarization curve and reveals the rate-limiting step to be *COOH to *CO at low overpotentials, CO$$_{2}$$2 adsorption at intermediate ones, and CO$$_{2}$$2 mass transport at high overpotentials. Finally, we show the Tafel slope to arise from the electrostatic interaction between the dipole of *CO$$_{2}$$2 and the interfacial field. This work highlights the importance of surface charging for electrochemical kinetics and mass transport.


1978 ◽  
Vol 39 (02) ◽  
pp. 496-503 ◽  
Author(s):  
P A D’Amore ◽  
H B Hechtman ◽  
D Shepro

SummaryOrnithine decarboxylase (ODC) activity, the rate-limiting step in the synthesis of polyamines, can be demonstrated in cultured, bovine, aortic endothelial cells (EC). Serum, serotonin and thrombin produce a rise in ODC activity. The serotonin-induced ODC activity is significantly blocked by imipramine (10-5 M) or Lilly 11 0140 (10-6M). Preincubation of EC with these blockers together almost completely depresses the 5-HT-stimulated ODC activity. These observations suggest a manner by which platelets may maintain EC structural and metabolic soundness.


Diabetes ◽  
1993 ◽  
Vol 42 (2) ◽  
pp. 296-306 ◽  
Author(s):  
D. C. Bradley ◽  
R. A. Poulin ◽  
R. N. Bergman

Sign in / Sign up

Export Citation Format

Share Document