Showing papers by "University of Jordan published in 2001"

Endoscopic exploration of Red Sea coral reefs reveals dense populations of cavity-dwelling sponges

Abstract: Framework cavities are the largest but least explored coral reef habitat1. Previous dive studies of caverns, spaces below plate corals, rubble and artificial cavities1,2,3 suggest that cavity-dwelling (coelobite) filter-feeders are important in the trophodynamics of reefs2,4,5. Quantitative community data are lacking, however, as the bulk of the narrow crevices interlacing the reef framework are inaccessible to conventional analysis methods6. Here we have developed endoscopic techniques to explore Red Sea framework crevices up to 4 m into the carbonate rock, revealing a large internal surface (2.5–7.4 m2 per projected m2 reef) dominated by encrusting filter-feeders. Sponges alone provided up to 60% of coelobite cover, outweighing epi-reefal filter-feeder biomass by two orders of magnitude. Coelobite community filtration removed more than 60% of the phytoplankton in the course of its less than 5-minute passage through the crevices, corresponding to an uptake of roughly 0.9 g carbon m-2 d-1. Mineralization of the largely allochthonous organic material is a principal source of nutrients supporting coral and algal growth. The supply of new material by coelobites may provide a key to understanding the ‘coral reef paradox’—a rich ecosystem thriving in nutrient-poor water.

Weed allelopathy, its ecological impacts and future prospects: a review

Abstract: Summary The importance, characteristics, positive and negative impacts, and future role of weeds as an integral part of the natural and agroecosystems are evaluated and discussed. Interference between plants in nature and the importance of differentiating between competition and allelopathy are interpreted. Allelopathy as one component of weed/crop interference, allelochemicals from weed species and their possible mechanism of action are listed and discussed. Weed species with inhibitory action against cultivated crops, other weed species, and plant pathogens, as well as self-inhibitory (autopathic) species are reviewed. Stimulatory or inhibitory allelopathic effects of different crop plants, trapping and catching species, and the potential of allelopathic weeds in inhibiting or stimulating certain parasitic weed species are discussed and evaluated. Allelopathy as a mechanism and future strategy for agricultural pest control and farm management and the potential use and development of some allelochemicals...

New K-Ar ages of basalts from the Harrat Ash Shaam volcanic field in Jordan: Implications for the span and duration of the upper-mantle upwelling beneath the western Arabian plate

Abstract: The volcanism in the western Arabian plate extends from the Red Sea through the Harrat Ash Shaam system to western Syria, as far north as the Bitlis suture in the Taurides. The Harrat Ash Shaam volcanic system in Jordan consists of northwest-trending dikes and a volcanic field that together encompass a width of 220 km. In terms of width, direction, and age of the main volcanic phases, the system is similar to the Red Sea dike belt. About 130 new K-Ar age determinations show that the ages of the Harrat Ash Shaam system (dikes and flows) range from Oligocene to Quaternary. However, there is a distinct gap in the ages between ∼22 and 13 Ma. This gap coincides with an apparent decrease in volcanism in the Red Sea region from around 20 to 12 Ma. We interpret this 9 m.y. gap as a quiescent period interrupting the volcanic activity in the region and suggest that from ∼22 to 13 Ma, tectonic activity in the Arabian plate was mainly restricted to the Red Sea region. A renewal of volcanism along the western margins of the Arabian plate at 13 Ma was very likely associated with the sinistral movement along the north-trending Dead Sea transform. This renewal of volcanism and tectonic activity may reflect the emergence of upper-mantle upwelling beneath the western Arabian plate at that time.

Perceived sources of stress among dental students at the University of Jordan.

Abstract: This study investigated perceived stress by dental students at the University of Jordan. Two hundred sixty-six students out of 290 completed a modified DES questionnaire. The stressors producing the highest ratings for perceived stress were examinations and grades, fully loaded day, and lack of time for relaxation. For the clinical years, patients' being late or not showing for their appointments and completing clinical requirements were also substantial stressors. Significant differences were found for eleven items across all classes and five items across clinical years. The overall perception of stress by students who had medicine as their first choice for admission was higher than for students who had dentistry as their first choice. Male-female comparison revealed significant differences for five items; between classes, significant differences were accounted for by three items. Comparison with earlier studies on identical questionnaire items revealed that perception of stress by Jordanian dental students was higher than for other students for items relating to educational environment and personal or cultural aspects.

The syndrome of chronic recurrent multifocal osteomyelitis and congenital dyserythropoietic anaemia. Report of a new family and a review.

Abstract: A new autosomal recessive syndrome of chronic recurrent multifocal osteomyelitis (CRMO) and congenital dyserythropoietic anaemia (CDA) with microcytosis has recently been described in four children (two sibships) of one consangineous Arab family. In this report, we describe the clinical features and course of the syndrome of CRMO and CDA in two additional patients (one sibship) from another consanguineous Arab family and review the literature. The two patients (brother and sister), the products of a consanguineous marriage, developed the syndrome at an early age of 3 weeks and 2 months respectively. The diagnosis of CRMO was confirmed by radiological and technetium isotope bone scans. Bone marrow studies confirmed the diagnosis of CDA. Peripheral blood films showed hypochromia and microcytosis. The sites involved by CRMO were periarticular, mainly around the elbow, knee, wrist and small joints of the hand. The brother is now 21 years old and the sister 3.5 years old and CRMO is still active with frequent relapses. The brother developed flexion deformities at the age of 13 years. Both patients failed to thrive; weight and height were below the 5th percentile. Conclusion: this is the second report of the syndrome of chronic recurrent multifocal osteomyelitis and microcytic congenital dyserythropoietic anaemia, confirming it as a clinical entity, inherited as an autosomal recessive trait. The disease is characterised by an early onset, long clinical course of remissions and relapses, and seems to be different from the sporadic form of chronic recurrent multifocal osteomyelitis.

Dissolved Oxygen, Chlorophyll a and Nutrients: Seasonal Cycles in Waters of the Gulf of Aquaba, Red Sea

Abstract: Seawater samples were collected weekly over fourteen months at 25 m intervals between the surface and 200 m from the offshore waters of the Gulf of Aqaba, Red Sea. Water temperature and dissolved oxygen concentration and percent saturation were measured in situ. Within two hours of sampling, samples were analysed for chlorophyll a , ammonia, nitrate, nitrite, phosphate and silicate. The temperature field depicted a well defined seasonal pattern of winter mixing from December to April and summer stratification from May to November. All other analysed parameters were intimately related to this pattern. Dissolved oxygen showed a maximum and homogeneous distribution in winter and a minimum in summer. Chlorophyll a showed a seasonal pattern close to that of dissolved oxygen, but with a distinct summer peak between 50 and 75 m. Ammonia was absent from the entire water column during summer and relatively abundant and homogeneously distributed in winter. Nitrite had a seasonal pattern similar to that of chlorophy...

Cephalometric norms in an Arabic population.

Abstract: Aim: To identify cephalometric norms for a Jordanian population.Design: A cross sectional study using a sample selected on the basis of a balanced face and a Class I occlusion.Materials and Methods: 65 subjects aged 14–17 years were selected from a larger sample on the basis of Class I incisors, a balanced profile and no previous orthodontic treatment. Lateral skull radiographs were digitised directly to produce values for SNA, SNB, ANB, UI/MX, LI/MN, UI/LI, MMPA and LI/A-Pog.Results: SNA and SNB were very close to the Eastman Standards. MMPA was significantly lower in Jordanians whilst UI/MX and LI/MN were significantly higher. Lower incisors were 4•6mm further forward in relation to A-Pog in Jordanians.

Selection of Barley Lines for Drought Tolerance in Low-Rainfall Areas

Abstract: An experiment was conducted at five locations in Jordan (Khanasri, annual rainfall 3 150 mm; Ramtha, 225 mm; Muwaqar, 150 mm; Rabba, 350 mm; Ghweer, 250 mm) during the 1996/1997 growing season, to evaluate the yield performance and some agronomic traits of 84 barley breeding lines and three long-term checks 4 (Zanbaka, Arta and Klaxon) for drought tolerance. An a-lattice design with two replications and six incomplete blocks for each replication was used. Genotype 6 (WI2291/Tadmor) was found to be superior in grain yield, especially compared to the best check (Arta) at the two wettest locations (Rabba and Ghweer). Genotype 21 (Mo.B1337/WI2291/5/ Emir/Sb//CM67/3/F8-HB-854-23/121//148-221/4/CI08887/ CI05761) out-yielded the best check (Arta) at the driest location (Khanasri), while genotype 61 (Salmas/Arabia Aswad) produced a higher grain yield than the best check (Zanbaka) at Ramtha. The correlations amongst grain yield, biological yield, straw yield, plant height and harvest index were always significant and positive regardless of the location. The correlations amongst days to heading, days to maturity and grain yield were significant at the two driest locations only. This suggests that diAerent phonologies are required to maximize grain yield in wet and dry environments. Also, the relationship between grain yield and the length of grain-filling period was positive in the wettest location (Rabba), negative in the driest (Khanasri) and not significant at the two intermediate locations. These results emphasize the importance of selection in the target environment and the need to develop early-maturing genotypes as a way of withstanding drought and high temperatures during the grain-filling period. A high and negative correlation coeAcient was found between the drought susceptibility index and grain yield at the driest site, whereas at the wettest site the correlation coeAcient was lower and in some cases positive, indicating the existence of traits that are desirable under drought and undesirable under favourable conditions.

The effect of implant diameter, restoration design, and occlusal table variations on screw loosening of posterior single-tooth implant restorations.

Abstract: The purpose of this study was to (1) determine in vitro the effect of narrowing the buccolingual width of the occlusal table on the untightening torque required to loosen gold prosthetic screws after subjecting implants and implant-supported restorations to occlusal loads, and (2) to compare the incidence of screw loosening and values of untightening torque of the screws among crowns supported by 1 wide-diameter as opposed to 2 standard implants after loading in vitro. The restorations were divided into 4 groups (group 1, a narrow crown supported by one 5-mm wide-diameter implant; group 2, a narrow crown supported by 2 standard 3.75-mm-diameter implants; group 3, a wide crown supported by one 5-mm wide-diameter implant; and group 4, a wide crown supported by 2 standard 3.75-mm-diameter implants). A custom-designed chewing machine was used to simulate the grinding phase of the masticatory cycle and lateral excursions. The crowns were subjected to a 6-kg load for 16660 cycles over 5.5 hours and were loaded at the outer and inner inclines and cusp tips with an untightening loading pattern. The untightening torque was measured for the gold screws in the different groups before and after loading at 4 different locations for 8 cycles on the simulated chewing machine. A 1-way analysis of variance indicated a significant difference (P < .001) among the test groups. Pairwise multiple comparison tests (Scheffe) were carried out on mean "change scores." Group 3 was significantly different from the other groups, which were not significantly different from each other. Restoring missing molars with 1 wide-diameter implant had a greater incidence of screw loosening as compared with 2 implants. Narrowing the occlusal table of the restoration is critical when using 1 implant to support a missing molar. The untightening torque of gold screws was not affected by changing the width of the occlusal table of crowns supported by 2 implants.

Si–N linkage in ultrabright, ultrasmall Si nanoparticles

Abstract: Ultrabright ultrasmall (∼1 nm) blue luminescent Si29 nanoparticles are chlorinated by reaction with Cl2 gas. A Si–N linkage is formed by the reaction of the chlorinated particles with the functional amine group in butylamine. Fourier transform infrared spectroscopy and x-ray photospectroscopy measurements confirm the N linkage and the presence of the butyl group, while emission, excitation, and autocorrelation femtosecond optical spectroscopy show that, after the linkage formation, the particles with the ultrabright blue luminescent remain, but with a redshift of 40 nm.

Ciliary Dyskinesia Associated With Hydrocephalus and Mental Retardation in a Jordanian Family

Abstract: Objective To describe the presentation and genetic transmission of ciliary dyskinesia syndrome associated with hydrocephalus and mental retardation in 3 generations of a family Patients and Methods A large Jordanian family included 9 individuals in 3 generations with recurrent pulmonary infections; 4 male siblings have been diagnosed as having mental retardation, and a maternal uncle was believed to have been similarly affected Chromosome analysis of the family showed a normal karyotype Results Electron microscopy of the nasal cilia from 3 affected siblings showed features of primary ciliary dyskinesia Computed tomographic scans of the brains of all 4 affected siblings showed hydrocephalus Conclusions The recurrent pulmonary infections and hydrocephalus in this large Jordanian family are likely related to ciliary dyskinesia, which appears to follow an autosomal recessive mode of inheritance The unusual presentation of ciliary dyskinesia, hydrocephalus, and mental retardation may be due to a new genetic mutation

Applying Modified Minimum Moment Method to Multiple Resource Leveling

Abstract: The purpose of this paper is to extend the modification of the minimum moment approach applied to networks with single resource leveling to networks with multiple resources. Specifically, the contribution of this paper is to outline a procedure to level multiple resources using the modified minimum moment approach. The heuristic procedure is applied to both methods of leveling multiple resources: leveling multiple resources in series and combined resource leveling. For comparison purposes, the proposed procedure is demonstrated through the same examples that were used to illustrate the use of the traditional minimum moment to both methods of multiple resource leveling. The application of the modified minimum moment approach showed the same results of the traditional minimum moment method. In some cases, the obtained results were even better than those of the traditional method.

Optimal prediction-intervals for the exponential distribution, based on generalized order statistics

Abstract: This paper proposes optimal prediction intervals for the future generalized order statistic (GOS) based on the first r GOS (ordinary order statistics, usual record values, k-record values) from an exponential population. A conditional argument is considered for obtaining an optimal prediction interval for future GOS. A numerical example illustrates this technique.

Variable parametric pseudo-rigid-body model for large-deflection beams with end loads

Abstract: This paper presents a variable parametric pseudo-rigid-body model for large-deflection beams with end loads. The values of the applied load ( P ) and joint stiffness of pseudo-rigid-body model ( k ) are expressed in terms of its kinematic parameters: the characteristic length ( γ ) and the “pseudo-rigid-body angle” (Θ). The expressions cover practical range of applications using a single equation for each variable. The accuracy of the expressions is excellent with correlation coefficients of (0.999) and (0.995). The accuracy of the end deflections generated by these expressions is shown to be much more greater than using the constant values for ( γ ) and ( k ). The new model is used for the analysis of two compliant mechanisms with different modes of analysis. The advantages of the new model and how it blends itself very smoothly in the analysis algorithm is illustrated through these examples.

Monitoring land use change in the Badia transition zone in Jordan using aerial photography and satellite imagery

Abstract: Detection of land use change makes a valuable contribution to the planning and monitoring of drylands. Land use changes at four sites within the Badia transition zone of Jordan were investigated and quantified over the period from 1953 to 1992 using black and white aerial photographs and SPOT PAN satellite imagery digitally merged with Landsat TM. Land use interpretation was checked in the field, and analysed using a Geographical Information System (GIS). Results indicated that land use changes have altered the character of the selected study sites. The important land use changes were from rangeland to rain-fed cultivation, irrigated fields and urban settlements. The increased agricultural activity was reflected in the land use maps through the 39-year period with the appearance of irrigated fields between 1978 and 1992. The land use changes are mainly attributed to the high population growth rate in Jordan and in the Badia, socio-economic change amongst Beduoin and farmers, the land tenure system and to a minor extent environmental factors.

Increased phosphorus mitigates the adverse effects of salinity in tissue culture

Abstract: Interactive effects of increased phosphorus (P) with salinity were studied at the microculture level of African violet (Saintpaulia ionantha) Increased P from 05 to 20 mM in the medium was very effective to mitigate the adverse effects of increased NaCl salinity (00, 50, 75, 100 mM) Growth (shoot height, and dry mass) was significantly reduced with increased salinity, whereas increasing P improved growth with elevated salt concentrations Leaf osmolarity was decreased (more negative) with salinity effect and it was increased (less negative) by P treatments Percent ash was increased with salinity and it was not highly affected by P Root number and root length were significantly reduced with increased salinity and improved with increased P The percentage of shoot content of nitrogen (N), P, calcium (Ca), potassium (K), and magnesium (Mg) were reduced with elevated salinity level and this reduction was less as P concentration increased in the medium Sodium (Na) was significantly increased with impos

Allelopathic Potential of White Top and Syrian Sage on Vegetable Crops

Abstract: However, the inhibitory materials may be autoinhibitory or heteroinhibitory (Kumari and Kohli, 1987), some White top [Cardaria draba (L.) Desv.] and Syrian sage (Salvia can be highly selective (Stachon and Zimdahl, 1980; syriaca L.) are noxious common weeds of field crops and orchards Sahid and Sugau, 1993), and their effect is concentration in Jordan. This study was conducted to investigate any allelopathic potential of volatiles, foliage leachates, root exudates, and shoot dried dependent (Qasem, 1993). residues of both weed species on cabbage (Brassica oleracea L. var. White top [Cardaria draba (L.) Desv.] and Syrian Capitata cv. Pronzwik), carrot (Daucus carota L. cv. Natus), cucum- sage (Salvia syriaca L.) are perennial rhizomatous and ber (Cucumis sativus L. cv. Beithalpha), squash (Cucurbita pepo L. root creeping weeds belonging to cruciferae and labiatae cv. Byrouti), onion (Allium cepa L. cv. Texas Early Grana), pepper families, respectively. They are widespread in cultivated (Capsicum annum L. cv. Red Common), or tomato (Lycopersicon fields in Jordan and invade field crops as well as oresculentum Mill cv. Special Back) through different laboratory and chards. Their deep, penetrating, hard, and extensive glasshouse experiments. Volatiles from Syrian sage fresh shoots re- creeping roots make them difficult to eradicate. If the duced germination and inhibited seedling growth of most crops, and weeds were left uncontrolled, they soon colonize a large foliage leachates or root exudates of both weeds were toxic to different area, choking the other plants present. Both are strong crops under laboratory conditions, with most effects on tomato and competitors for soil moisture in arid regions, and their cabbage. In pot experiments, surface-placed shoot residues of both growth increased with increasing water consumption weeds significantly delayed seed germination and reduced seedling growth of all crops with carrot, onion, and tomato being the most (Al-Ahmed, 1982; Qasem and Abu-Irmaileh, 1983). affected. Decayed residues of white top were also toxic at 32 g kg 21 , Furthermore, both weed species have been reported but lower toxicity was obtained than when fresh materials were used. to possess high allelopathic activity against crops, includFoliage leachates or root exudates of both weed species added or ing wheat (Triticum aestivum L.) and barley (Hordeum released into the soil mixture reduced seedling growth of cabbage vulgare L.) (Qasem and Abu-Irmaileh, 1985; Qasem, and tomato. Results showed that white top and Syrian sage are of 1993, 1994). When shoot and root extracts, water leagreat allelopathic potential against different vegetable crops; cabbage, chates, and dried residues of both weeds were added to onion, and tomato being the most sensitive crops. the soil, all inhibited germination, growth, and development of these crops. The objective of the present work was to investigate M anynoxious annual and perennial weeds have any possible role of allelopathy mechanism in the interbeen regarded as species with allelopathic poten- ference between these two common and noxious weed tial and can severely affect crop survival and productiv- species (through their possible volatile materials, root ity (Putnam and Duke, 1978; Rice, 1979; Qasem, 1994). exudates, foliage leachates, and shoot residues) on gerAllelochemicals produced by plants may be released mination and growth of their associated vegetable crops. into the surrounding environment in sufficient amounts with enough persistence to affect neighboring and suc