Vol. 11 Issue 3

Adnan A.S. Jibril
The almost unitarily equivalence relation, ϴ, between operators is defined. It is shown that some properties are shared by almost unitarily equivalent operators. Various results related to ϴ are proved.

M.A. AI-Gwaiz and V. Anandam
A necessary condition for a subharmonic function in IRn to have a non-constant harmonic minorant is obtained. This result is shown to be a variation of Bocher's theorem in IRn.

Ibrahim S. Al-Naimi, Hatif A. Aishirayda and Khalid G. Aladely
A new series of heterocyclic tellurium dialkoxides (CnH2nTe (OR)2: n = 4, 5, R = CH1CH2CH1, CH2CH2CH, and n-But.) have been prepared by the reaction of sodium alkoxides with the corresponding cyclic tellurium diiodide. These compounds were characterized on the basis of their IR, 1H NMR and Mass spectral data. Conductivity measurements in DMSO and DMF have shown a considerable ionic behaviour

Ibrahim S. Al-Naimi, Hatif A. Aishirayda and Khalid G. Aladely
A new series of heterocyclic tellurium dialkoxides (CnH2nTe (OR)2: n = 4, 5, R = CH1CH2CH1, CH2CH2CH, and n-But.) have been prepared by the reaction of sodium alkoxides with the corresponding cyclic tellurium diiodide. These compounds were characterized on the basis of their IR, 1H NMR and Mass spectral data. Conductivity measurements in DMSO and DMF have shown a considerable ionic behaviour

Abdulaziz A. El-Sulaiman, Abdulrahman M. Alamoud, Abobakr S. Ahmed and Mohammad I. Qureshi
The effect of reduced pressure on the DC quasi-steady state and discharge activity in hydrocarbon oils has been studied experimentally. Nonuniform high DC field is applied to fresh and aged transformer oil and liquid paraffin sample. The applied pressure is reduced from about 133 to 6.6 kPa and then increased vice versa for each applied voltage inside a controlled vacuum chamber. At a fixed voltage level the quasi steady state current is found to remain almost unchanged with pressure reduction down to a certain critical sub-atmospheric pressure, where after the current behavior is different for different oils, It increases or decreases sharply for transformer oil and liquid paraffin respectively. The value of this critical pressure increases as the applied voltage is increased. Reduction of pressure has similar effects on discharge activity as well. The experimental results suggest that vaporization and molecular structure of oils play an important role at sub-atmospheric pressure.

A.S. Kassem, A.M. Mujahid and D. W. Turner
A daily average diffuse sky radiation regression model based on daily global radiation was developed utilizing two year data taken near Blytheville , Arkansas (Lat. = 35.9°N, Long. = 89.9°W), U.S.A. The model has a determination coefficient of 0.91 and 0.092 standard error of estimate. The data were also analyzed for a seasonal dependence and four seasonal average daily models were developed for the spring, summer, fall and winter seasons. The coefficient of determination is 0.93,0.81, 0.94 and 0.93, whereas the standard error of estimate is 0.08, 0.102, 0.042 and 0.075 for spring, summer, fall and winter, respectively. A monthly average daily diffuse sky radiation model was also developed. The coefficient of determination is 0.92 and the standard error of estimate is 0.083. A seasonal monthly average model was also developed which has 0.91 coefficient of determination and 0.085 standard error of estimate. The developed monthly daily average and daily models compare well with a selected number of previously developed models

H.E. Osman
Field experiments were conducted for 3 years to determine the effects of cultivar, nitrogen and plant population on seed yield and other plant characteristics under the conditions of limited water supply in rain fed areas of the central Sudan. Seed yield and its components were adversely affected by delayed sowing and inadequate water supply. Cultivar, unlike nitrogen and inter-row spacing, had a significant effect on seed yield, plant height and number of capsules plant- I under favourable environments (i.e. early sowing and adequate moisture). In the dry season, cultivars differed significantly in days to flowering whereas nitrogen significantly increased number of days to onset of flowering and increased number of capsules plant-I. Cultivar x nitrogen and cultivar x spacing interactions varied with the season and the plant parameter but they were both significant for number of plant ha- I in the dry and moderate seasons. Interactions of cultivar x nitrogen were also significant for seed yield in both favourable and moderate seasons and for number of capsules and plant height in the fonner. In the favourable environment cultivars UCR 76202 (1388 kg ha-1 ) and UCR 75370 (979 kg ha -1) had their highest seed yields (71 and 56% over the control) at 40 kg N ha -1; whereas the local cultivars A/5/9 (1183 kg ha-1) and A/1/9 (1057 kg ha-1) had their highest yields (22 and 14% over the control) at 20 and 80 kg N ha--1, respectively.

A.A. Al-Khalifa and R.M. Mahmoud
Since polyphenol oxidase (PPO) plays the key role in enzymatic browning of potatoes, five potato varieties produced in Al-Kharj region, Kingdom of Saudi Arabia, were evaluated for PPO activity. Wide variations in PPO activities among the different potato varieties were found . Ajax potato variety was very low in PPO. Extensive cultivation of low PPO potato varieties should be encouraged. Characteristics of potato PPO extract were also investigated. The temperature and pH optima for the enzyme we re 30-40°C and pH 7, respectively. Heat stability studies indicated that a complete inactivation of PPO occurred at 800C for 30 min. Regarding the effect of inhibitors on the enzyme. sodium metabisulfite and ascorbic acid were the most effective. whereas sodium chloride and EDTA were the least.

Fawzi M. Karim
Recent extensive floristic collections from U.A.E especially the Al-Ain, Dhaid and Hatta districts in the east of the country, revealed the presence of 10 new taxa of the Flora of U.A.E. These are: Alternanthera pungens (Amaranthaceae), Ogastemma pusillum (Boraginaceae), Lepidium sativum (Brassicaceae), Cleome viscosa (Capparidaceae), Euphorbia dracunculoides, Euphorbia falcata, Euphorbia helioscopia (Euphorbiaceae), Malva nicaeensis (Malvaceae), Lolium persicum (Poaceae), Portulaca quadrifida (Portulacaceae).

A.S. Ramadani and A.M. Aggab
The growth, both radial and as biomass expressed by 13 fungal species from alkaline soils at two localities in the Makkah district was studied. No obligate alkaliphile was found but facultative alkaliphile was shown by Cylindrocarpon heteronemum and Acremonium strictum, while Fusarium moniliforme appeared to be highly alkaline-tolerant. Fast growing fungi such as Rhizopus nigricans, Cunninghamella elegans, Rhizoctonia solani and Arthrobotrys oligospora were alkaline-sensitive. Slower growing species were, on the other hand, alkaline-tolerant. A positive correlation was found between the level of alkaliphile and the frequency of occurrence in Saudi soils of the Makkah district.