Vol. 8 Issue 2
Tahsin Ghazal
The vanishing of the differentials of the Atiyah-Hirzebruch spectral sequence on the Thom class is the necessary and sufficient condition for O(n)- bundle to be orientable with respect to a cohomology theory h*. It is shown here that the third Stiefel-Whitney class is the first obstruction for an oriented spherical fibration to be orientable with respect to mod 2 K-theory K* ( ;Z/2). By killing the third differential of the Atiyah-Hirzebruch spectral sequence, we will find the second obstruction for an oriented real vector bundle to be orientable with respect to K* ( ;Z/2) by calculating the fifth differential in the Atiyah- Hirzebruch spectral sequence
Abdulrahman S. Attiyat
Flame spectroscopy has been used to monitor net changes in concentration of dilute solution of thirty four elements at different concentrations in Pyrex, soft glass, and polyethylene containers for periods up to one year or more.
R.J. Tag, M. Abu-Ouf and A. El-Shater
Grain-size variation of sediments in different environments of the coastal zone between Wadi Al-Fagh and Wadi Al-Qunfidah, eastern Red Sea were studied. The wadi sediments are generally muddy gravely sand exhibiting a general downstream decrease in the mean grain-size. The bed material of wadis in the northern part of the study area is markedly finer than that of wadis in the southern part, where gravel-sized sediments are more common. The sediments distribution reflects short-lived flood flow patterns in the wadis. The remarkable changes in the texture characteristics of sediments of the northern wadis are considered to be due to the rainfall increase to the south. The dune sands of eolian origin are well to moderately sorted with a narrow range in the mean size (1.92- 2.85Ф).
Generally, the beach sediments are medium to fine sands, well to moderately sorted and to a great extent negatively skewed. The intertidal and subtidal sediments both exhibit a wide range of textural characteristics.
The intertidal sediments are generally coarser than those of subtidal zone. Also in the south of the studied region, sediments from the tidal zones in the deltas fronting wadis Al Dugh, and Ahsibah, are markedly coarser than elsewhere in the region. In the north of the area the relationships appear to be different particularly with respect to the intertidal sediments where the sediments from between the wadis is coarser than that in front of the wadis.
The terrigenous sediments from the wadis are mixed with locally produced carbonate in varying proportions in the beach and littoral zones. Such mixing and subsequent reworking by the nearshore processes result in the observed variation in texture. There does not, however, appear to be any correlation between mean size and the relative proportions of the carbonate to terrigenous material in the sediments
H.S. Al-Yousefi and S.S. Udpa
This paper introduces a new approach for segmenting handwritten Arabic characters to improve the recognition of these characters. The proposed approach involves, as a first step, digitization of the segmented characters. The dots and zigzags (secondaries) are then segmented and identified separately. This reduces the recognition issue from a 28 to a 20-class problem. The recognition of the primary part of the characters is achieved using features derived from the moments of the horizontal and vertical projections normalized with respect to the zero-order moment. Classification of the primary characters is accomplished using quadratic discriminant functions. Results showing considerable improvement in classification are presented.
I.M. Fouda, M.M. El-Tonsy and K.A. El-Farahaty
Application of Becke-line, double-beam and multiple-beam interferometric methods were used to measure the refractive indices and birefringence of Saudi (Gizan) cotton fibres. The scanning electron microscopy was used to estimate the cross sectional parameters and to show deformations and fine fibrillar structures which cannot be resolved with optical microscopes on the fibre surface. The resulting data were utilized to calculate the polarizability per unit volume, Cauchy's dispersion constants, dispersive power, isotropic refractive index, the spiral angle, the optical orientation angle and specific volume of the fibre materials. The results were found in good agreement with the previously published values of different varieties of cotton fibres. Micro-interferograms are given for illustrations
M. Reda and A.S. Modaihsh
Soil column experiments were conducted to evaluate the effect of different rates of sulphur application on gypsum formation in calcareous soils. Elemental sulphur was applied to three soils at the rate of 0.5%, 1.5%, and 3.0%. Soils columns were incubated at 30°C for 3, 6, 9 and 18 weeks and were intermittently leached with distilled water. Thin soil sections were microscopically examined to detect and evaluate gypsum formation in soils. Chemical analysis of gypsum was also used for the same purpose. Gypsum, as anisotropic anhedral aggregates, was noticed with thin sections in all sulphur treated sois. Formation of gypsum was confined to the uppermost 10 cm and was optically recorded after 9 and 18 weeks of incubation treatments for two of the Soils, of Al-Qasseem and Derab at all periods of incubation for the Al-Kharj sandy soil. These findings were in agreement with the chemical data which showed the same trend. The second level of sulphur (1.5%) application is highly recommended as most of it can be oxidized after 9-18 weeks.
Mohammad Abdel-Razik
The productivity and nutrient cycling are evaluated in a clover desert agroecosystem under the conventional rotational grazing. A descriptive model of the state of the system that integrates the collected information is presented.
The annual total production of clover is estimated as 16.65 tonnes per hectare, while that of the associated weeds is about 2.41 tonnes per hectare. The temporal variations in biomass and nutrient content in different system components are promoted by defoliation by grazing animals. Most resources are manipulated by both shoots and roots during the growing season, which allows for a turnover ration of about 30% of annual production (surplus for long term ecosystem maintenance), and consequently to positive net ecosystem production levels. Therefore, clover with minimum subsidy of irrigation water may be one of the best crops to be raised under arid conditions. It serves a multiple conservation purpose by releasing grazing pressure on natural range lands and fields of the Nile Delta and improving the nutrient status and soil structure of the desert lands
A.A.M. Al-Jibouri, F.A. Fattah, I.S. Alsaadawi, M. Selbi and M. Kgazal
Pollen of seven staminate cultivars of date palm were collected from Al-Zafarania Agricultural Experimental Station, Baghdad and studied for pollen germination, pollen tube growth, number of pollen grains per flower and pollen morphometrics. The pollen was also examined by scanning electron microscopy for morphological differences in exine structure.
Significant differences were found among the test cultivars in all the parameters tested. The highest pollen germination and pollen tube growth was observed for cv. Green Ghanami and the lowest was found in cv. Wardi. The greatest number of pollen grains was recorded in Green Ghanami flowers and the lowest in Red Ghanami.
Scanning electron microscope study of pollen of the test cultivars revealed overall similarities in shape and size. The pollen grains are monosulcate, elliptical with one central closed germinal furrow. Exine of the test cultivars showed a tectate perforate pattern with considerable variations in the shape of the sculpturing appearance.
Naheel F. Dajani, Rashad M. Natour, Abdulazim S. Salhab and Adel Mahasneh
Zearalenone and zearalenone producing fungi were sought in 326 feed samples of 12 different types of cereals and animal feedstuffs collected from different localities in Jordan during March 1986 to April 1987. Some tested samples harboured zearalenone with a concentration range of 0.9- 3.5 ppm. In commercially prepared animal feedstuffs and feed concentrates used for sheep, fish, layers, poultry and cows, zearalenone was detected at a level of 0.47- 4.0 ppm. On the basis of microscopic and morphological identification, 77 isolates of the Fusarium spp. were obtained. Eleven representative isolates were identified and confirmed by the Commonwealth Mycological Institute, Kew, England. The isolates belonged to Fusarium moniliforme Sheldon and Fusarium moniliforme var. inter. Thirty seven of the mentioned Fusarium isolates were examined for their ability to produce zearalenone under laboratory conditions and only 9 (25.7%) produced zearalenone at an average level of 0.78 ppm.
Robert C. Bullock
Three large species of Chiton reported from the Arabian Sea region, C. peregrinus Thiele 1910, C. salihafui Bullock 1972, and C. fosteri Bullock 1972, were examined to determine their taxonomic position within the subfamily Chitoninae. Radular morphology of these species, especially the centrolateral tooth with a distal end parallel to the longitudinal axis of the animal and the major lateral tooth with a short denticle cap oriented 90° with respect to the tooth shaft, indicates that these species belong in the genus Rhyssoplax, not in Chiton.