Vol. 2 Issue 2
T. El-Dessouki and H. El-Ghandour
The characteristics of interference pattern for single and double interference holograms were compared to those of two separate identical diffusers. Several advantages over the system of two parallel identical diffusers were found.
A.A. AI-Saleh and Mohammad A. Khan
The diplord (2n) chromosome number of Meriones libycus syrius from Saudi Arabia is 44; the fundamental number (FN) is 78 and the fundamental number of autosomes (FNa) is 74. The autosomes consist of 11 pairs of metacentric, 5 pairs of submetacentric and 5 pairs of acrocentric chromosomes. The X chromosome is the second largest metacentric and the Y is the smallest metacentric element. These findings differ from those previously published for this species.
N.A. AI Asgah
A review of the effects of salinity on the early stages of fish is given, and methods used to study the effect of salinity on percentage of egg hatching and survival of Oreochromis niloticus (Linnaeus) larvae are described. Eggs of O. niloticus fertilized in a natural salinity of 2.1% were tested for hatching and for survival of the larvae in five salinity concentrations of 5, 10, 15, 20 and 25%. Results show that successful egg hatching could be obtained at salinities up to 20%. Two lethal limits are also reported: at salinity 25% for larvae hatched in salinities 5, 10 and 15%; and at salinity 30% or those hatched in 20%. Both the two lethal limits were found to be extended to higher salinity by acclimation of the larvae.
Kh.A. Hussein
Samples of ovaries of Tilapia nilotica collected monthly from Lake Manzalah (Egypt) confirm that the female lay eggs in batches, hence is partial spawner. The number of such batches varies from 4 to 5. The nearly ripe eggs are pear shaped, surrounded by a thick layer cytoplasm directly beneath the outer covering layer (oolemma).
A peculiarity of oogenesis of T. nilotica is the continuous resorption of oocytes in different stages of maturation, even up to the times of ripening. Resorption occurs not only during trophoplasmic growth but also during the period of protoplasmic growth. Reduction in egg number by consecutive resorption greatly affects the calculation of final fecundity. Percentages of resorption and consequently the decrease in the number of oocytes in each stage are correlated primarily with the size of oocytes and also with the size of the ovary itself and finally with size of each batch ready to shed.
A.M.N. Kalantan and Misbahul Arlin
The chemical nature of clamp sclerites of the monogenetic trematode Heteromicrocotyle indicus parasitizing the gills of the marine fish Carangoides bajad was investigated using histochemical techniques. Both types of clamp sclerites are stabilized by the formation of bimers of tyrosine and basic proteins are also present. In addition, the clamp material gives positive reaction to elastin stains. Other structural proteins such as collagen, proteins having-S- containing amino acids and sclerotin are absent
S.Z. Hyder, M.A. Al-Thamari and Saud Al-Eyyed
To determine the possibility of introducing Leucaena leucocephala into saline areas of Saudi Arabia, observations were made on the effect of salt stress on germination and seedling development of this species. Germination percentage and rate were both reduced in the presence of various monovalent and divalent ions. Monovalent ios were more inhibitory than divalent ions for germination percentage and germination rate. Germination of Leucaena leucocephala was more tolerant to these ions than seedling development. Salinity reduced root growth more than sheet growth and ions accumulated in plant tissues to toxic levels. It was concluded that like other legumes, Leucaena leucocephala is salt sensitive and may not prosper in those regions of Saudi Arabia with high salinity.
Pardul Khan, A.A. Barakat and S. AI-Salem
Malathion is being widely used for pest control on vegetable crops in Saudi Arabia. Studies were initiated to determine the levels of malathion residues on lettuce, cucumber and tomato plants at different intervals after the application of malathion. Foliage and/or fruit samples from treated and untreated plants were extracted for the residue analysis by gas- liquid chromatography.
The initial amounts of malathion residue and their subsequent decrease after spray varied among the three vegetable crops. Moreover, the level of residues in lettuce was higher in the greenhouse than in the field. The half-life values of malathion were about1 or 2 days for the tested vegetables. The residues of malathion in cucumber and tomatoes even at 0 hr after spray were well below the 'established tolerance levels', while that of lettuce was 23 ppm. However, the residue level of malathion in lettuce subsided well below the critical limit at 5 days after application.
O.A. Hamed and G.A. Sorial
Experimental investigations for the effect of jetwise flow of condensing steam on a single vertical tube have been carried out. The variables covered included orifice diameter, heat load and steam velocity. Particular emphasis has been laid on making direct comparison between normal flow of vapour and high jet vapour velocities.
It has been found that the streamside coefficient of heat transfer was increased by the jetwise flow to values of 2.0 to 9.55 times the value for stationary vapour. The corresponding vapour pressure loss to induce the jetwise was 4.7 and 50.0 cm Hg, respectively.
The high dependence of the heat transfer enhancement on the jet driving force is presented. The jetwise flow approach may find direct applications in industries where high pressure steam is available.
Abdul-Halim A.K. Mohammed and Nihad Abbas
A laboratory coking unit was designed and constructed for the experimental study of the delayed coking process of spent oil distillate. The yield and analysis of coke, gases and liquid products were obtained for each experiment. The study showed that spent oil distillate produced relatively low sulphur content coke and with no metals. Increasing the recycle ratio increases the coke yield and decreases the gas and gasoline yield and the olefins content of gasoline. The recycle ratio has a slight effect on the sulphur content of produced coke.