Higher Ea Values Research Articles

Evaporation values in East Africa

Potential evaporation (Ep) and actual evapotranspiration (EA) values for 84 East African stations were estimated and mapped using Morton [12, 13, 14] model. The data used in the study were long term averages up to and including 1974. TheEp andEA distributions for the months of January, April, and July and October; and annual are discussed. HighEp values exist in the semi-arid/arid areas of northern and northeastern Kenya and central Tanzania. LowEp values dominate on the highland areas. HighEA values are observed over the East African rainfall favoured and thickly vegetated areas whereas the lowestEA values are predominantly observed during all months in semi-arid/arid areas. BothEp andEp values show a good agreement with the north/south movement of the rain belts across East Africa.

Catalytic activity of CoO–ZnO–MgO solid solutions for the decomposition of N2O. Role of the matrix

The catalytic activity of CoO–ZnO–MgO solid solutions, MZCo x:y(x= 0.1–30 Zn atoms per 100 Mg atoms and y= 1–10 Co atoms per 100 Mg atoms), has been investigated for N2O decomposition in the temperature range 490–750 K at a pressure of ca. 8 kPa (60 Torr). The turnover frequency, Nion(molecules decomposed per Co ion per second), decreases with increasing zinc content (matrix effect). It also decreases with increasing cobalt concentration, more markedly at low zinc content (dilution effect). The apparent activation energy Ea increases with increasing zinc content. A comparison of the present data with earlier data on CoO–MgO, Mg1–xCoxAl2O4 and CoO–ZnO systems leads to an interpretation of the catalytic behaviour. The detrimental effect of zinc on Nion values is explained by the setting up of reaction steps which involve the formation of strongly-bound oxygen species not suitable for desorption at low temperature, and responsible for the higher Ea values.

Melt viscosity characteristics of methacrylate–styrene copolymers

AbstractThe activation energies of flow EA of methacrylate–styrene copolymers containing n‐butyl, n‐hexyl, n‐heptyl, n‐octyl, n‐decyl, n‐dodecyl, n‐tridecyl, n‐octadecyl, and cyclohexyl methacrylate have been investigated as a function of molecular weight, composition, and methacrylate monomer. Below a critical pendent group molar volume per chain unit (120 ± 10 ml Le Bas units), EA was found to increase with molar volume; and above this value, a decrease in EA was observed, reflecting a decrease in copolymer density. Copolymers with pendent group molar volumes per average chain unit of between 96 and 140 ml (Le Bas units) were found to exhibit sufficiently high EA values to render them suitable for use in thermoplastic and photothermoplastic devices with superior development and erasure rates, at temperatures which enabled the attainment of the development and erasure viscosities with a low expenditure of heat energy. Methacrylate–styrene copolymers with long‐chain ester methacrylates (viz., n‐decyl and n‐dodecyl methacrylate) were found to exhibit critical molecular weights Mc below 3000; and Mc was found to decrease with increasing methacrylate tail length and methacrylate concentration. These Mc values correspond to critical chain lengths Zc below 45. Similar Zc values have been previously reported for acrylonitrile–methyl methacrylate copolymers30 and ethylene–propylene copolymers.28

Kinetics of Thermal Destruction of Bacteriophages Active Against Streptococcus lactis

The kinetics and thermodynamics of the heat inactivation for bacteriophages active against Streptococcus lactis C2 and C10 were determined in skimmilk. Thermal destruction of Phage c10 at 55, 60, and 65C and Phage c2 at 55C followed the kinetics of a first-order reaction. However, at 60 and 65C, the thermal destruction of Phage c2 failed to follow the kinetics of a first-order reaction. At 60.2C, the rate of heat inactivation of Phage c10 and the second component of Phage c2 was the same. The D, k, and ΔF values for Phage c2 would indicate that it is more heat stable above 60.2C and less heat stable below 60.2C than c10 phage. Based on the high positive Ea and ΔS values, it would appear that protein and nucleic acid denaturation is associated with the thermal inactivation process for Phage c10. In contrast, for Phage c2, low positive Ea and negative ΔS values indicate that the thermal inactivation of this phage at the temperatures studied involves a single point of attack of the deoxyribonucleic acid strand or a disorientation of a decisive protein.