Showing papers by "University of Jordan published in 1977"

Low-energy He-He interactions with phenomenological potentials

Abstract: The low-energy atom-atom scattering properties are studied for various combinations of He isotopes interacting via a family of semiphenomenological potentials. Some of the potentials bind the (4He)2 molecule and some do not, and it is observed that molecular beam scattering measurements at energies currently accessible cannot resolve the difference between the two types of potentials. Our results are discussed within the framework of possible measurements to resolve this discrepancy. We present a method for solving the Schrodinger equation which is uniformly applicable for both bound and scattering state solutions and which is particularly suited to the types of potentials describing interactions for the rare gas atoms.

Phase diagram of electron-beam codeposited Nb 3 Ge: The influence of oxygen and other gases

Abstract: Oxygen, air, or chlorine gas present in the vacuum system during evaporation extend the Ge-rich boundary of the A15 phase towards the ideal 3:1 ratio. X-ray evidence indicates the presence of an amorphous component below 775°C which is detrimental to the superconductivity and which is accompanied by an abrupt increase in the A15 lattice constant. Preliminary Auger results indicate that the Nb:O ratio first decreases as the partial pressure of O 2 increases and then remains constant.

Deformation band studies of oriented polyethylene and polyethylene terephthalate

Abstract: Deformation bands formed at the yield point in tensile tests on oriented high-density polyethylene have been studied by optical microscopy and wide-angle x-ray (WAXS) diffraction. The observations of the rotation of the optical extinction direction are shown to obey a simple scheme proposed previously by us: the principal directions of the refractive index ellipsoid within the deformation bands are everywhere parallel to the principal axes of the plastic strain ellipsoid, zero strain referring to the isotropic state. This result is similar to that obtained previously for polyethylene terephthalate (PET) and polypropylene despite the much higher crystallinity obtained with polyethylene. Independent measurements of the molecular reorientation in the deformation bands made using wide-angle x-ray scattering broadly confirm the optical measurements. The results taken together suggest that the material within the band, whether crystalline or not, becomes realigned about the new direction of maximum elongation as if controlled by the deformation of an effective molecular network.

Weed Control in Wheat and Barley in the Middle East

Abstract: Wheat and barley constitute the bulk of agricultural production in the Middle East. Unfortunately, these crops are grown on marginal soils which are infested with annual and perennial weeds. The principal weed species include Avena sterilis L., Convolvulus arvensis L., and Sinapis arvensis L. and it has been estimated that yield losses due to weeds are between 20 and 30%. Control is mostly by hand pulling, hoeing or mechanical tillage, the use of herbicides being limited to about 2–5%, of the cereal area. The chemical used is usually 2,4-D but there are a few applications of barban. With the increase in wages, and unavailability of agricultural labour it is suggested that herbicide application should be widely used in the Middle East. Mixtures with benzonitriles and dicamba should be used in addition to the economical phenoxy herbicides to widen the spectrum of control of broadleaved weeds. Glyphosate may also be used after grain harvest for the control of perennial weeds and tri-allate, chlortol...

Production of mosaic lethals in different germ cell stages of drosophila by N-methyl-N'-nitro-N-nitrosoguanidine.

Abstract: The delayed effect of N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) was studied in Drosophila melanogaster by the proportion of mosaic progeny produced after the treatment Following injection of the chemical into wild type males, complete and mosaic sex-linked recessive lethals were scored by the Muller-5 method, in five successive broods representing the different stages of spermatogenesis All broods showed significant increase over the control in the frequencies of complete lethals with gradual decrease in mutation rate from the post-meiotic stages to the pre-meiotic ones In the case of mosaic lethals, too, the post-meiotic stages were generally more sensitive; but the increase over the control was significant only for the mature spermatozoa The extension of the experiment to F4 generation showed that a mosaic F1 female may produce further mosaic progeny The production of lethal mutations in successive generations after treatment with MNNG supports the view that chemically induced instabilities can be transmitted as such over several generations

Records of Tabanidae from Azraq Oasis, Jordan

Abstract: Little is known about the occurrence and distribution of arthropods of medical and veterinary importance in Jordan. Mosquitoes vectoring the causal agents of human malaria are probably the only species satisfactorily studied. Reported here are records of Tabanidae from marshes of the Azraq Oasis, the only permanent body of water in the Jordanian desert, some 100 km east of Amman. The marshes receive water from 2 large freshwater springs in the oasis. The salinity of water in the marshes where tabanid larvae were observed ranged from 0.69–2.72 g/liter depending on the nature of the soil, season of examination (highest during summer) and distance from the springs. Animals including cattle, camels, sheep and horses are raised in the area or are brought in by Bedouins for water and grazing. Animals graze in the marshes all year round.

The Effectiveness of Programmed Instruction in Teaching English at the Secondary School Level

Abstract: One hundred Jordanian boys were arranged in two matched groups to study the effectiveness of programmed instruction in teaching English at the secondary school level compared to regular classroom teaching. Utilising a ‘t’ test and a 2 x 2 analysis of variance the results indicated the superiority of PI compared to regular classroom teaching. All main effects (method and ability) and three interaction effects were significant. Students low in achievement seem to have benefited more from PI than from regular classroom teaching. These results were interpreted on the basis of the inherent qualities of PI such as structuring the learning situation and providing immediate knowledge of results, which are lacking in regular classroom teaching.