Showing papers by "King Saud University published in 1985"

Effect of Antibiotics on Adherence of Microorganisms to Epithelial Cell Surfaces

Abstract: Microbial adherence to epithelial cell surfaces has been implicated as the first step in the initiation of several infectious diseases. Subinhibitory concentrations of antibiotics affect the adherence properties of microorganisms in various ways. They can inhibit the expression of fimbriae and the synthesis of other surface components, and they may also cause the release of constituents from the cell. The ability of antibiotics to affect the properties of microbial adherence to cell surfaces may be an important criterion in selecting an antibiotic for therapy.

High-Field Distribution and Mobility in Semiconductors

Abstract: A first-principles theory of carrier distribution in the presence of an electric field of arbitrary strength, which takes into account the quantum-mechanical field-broadening, is described under conditions that the acoustic-phonon scattering is the dominant mechanism of scattering. The general expression of the mobility so obtained reduces to its Ohmic value for vanishing small electric fields, is a quadratic function of electric field in the warm-electron regime, and varies inversely with the electric field at sufficiently high electric fields (hot-electron regime). A saturation current is obtained in the high-field limit, when electron mobility is limited solely by the field-broadening effect; the saturation velocity being comparable to the thermal velocity of an electron. The hot-electron temperature, defined in terms of average energy of an electron, is equal to the lattice temperature in the Ohmic regime, rises quadratically with the increasing electric field in the warm-electron regime, and rises linearly in the hot-electron regime. These results are in agreement with those of experiments on n-Germanium.

Diversity of salt tolerance in a germplasm collection of wheat (Triticum spp.).

Abstract: A collection (5,072 lines) of wheat germplasm was screened at the seedling stage for tolerance to salinity concentrations having electrical conductivities of 0.8 (control), 12.5, 18.75 and 25.0 dS/m. Surviving seedlings were expressed for each line as a percentage of the control value. The 442 lines with greater than 70% surviving seedlings were tested for whole-life cycle survival under each salinity condition. The data of the reactions to salinity at both the seedling stage and maturity were used to classify the collection according to: (1) country of origin (2) species and ploidy level. The data were then subjected to a diversity analysis using the Shannon-Weaver information index. Seedling stage tolerance to 12.5 dS/cm salinity was widely distributed in the collection (79% of lines), whereas only 9% were tolerant at 25.0 dS/m salinity. The seedling stage tolerance was indicative of maturity tolerance. At the seedling stage, entries from USA and Egypt showed the largest proportions of tolerant lines. In addition, USA, Mexico and Egypt entries exhibited the widest variability. Diversity among regions was greater than among countries within regions, while the diversity among species was greater than among ploidy levels. Tetraploids exceeded hexaploids and diploids in the proportion of tolerant lines and diversity. Wheat-rye derivatives showed a good potential for salt tolerance at early stages. Screening more germplasm from the arid and semi-arid regions especially from countries with salt affected soils was recommended.

Probiotics in Poultry Nutrition—A Review

Abstract: The commercial use of probiotics in the livestock industry, especially poultry, is relatively new. Only within the last few years have research workers documented the results of incorporating probi...

A Study on the Crude Antidiabetic Drugs Used in Arabian Folk Medicine

Abstract: A survey of different regions of Saudi Arabia revealed that a large number of herbal drugs are used for the treatment of diabetes in the traditional medicine of this country. Twelve of these antidiabetic plants were collected and identified. The literature was surveyed to find distribution, chemical constituents and other medicinal uses of these plants. Studies for antidiabetic activity in alloxanized mice in our laboratory showed that out of 12 plants, three plants (Teucriurn Oliverianum, Hammada saticornica and Allium cepa) possess significant oral hypoglycemic (25% to 38%) activity; three plants (Artemisia abyssinica, Azadirachta indica and Loranthus curviflorus) showed moderate (11% to 23%) activity. Five plants (Rhazya stricta, Momordica churuntia, Aloe Vera, Allium sativum and Coriandrum sativum) were found to possess no significant activity. One plant (Moringa oleifera) rather increased the blood glucose (15%) in diabetic mice.

Phonon-scattering-limited mobility in a quantum-well heterostructure.

Abstract: The theory of electron-lattice scattering is examined for a quantum-well heterostructure in the size quantum limit when most of the electrons populate the lowest quantized subband. The acoustic-phonon scattering is found to be one of the important mechanisms of scattering at intermediate temperatures when donors supplying the electrons are removed in an adjacent nonconducting layer.

Harmonic oscillator with strongly pulsating mass under the action of a driving force.

Abstract: The exact solution for the problem of a harmonic oscillator of frequency ${\ensuremath{\omega}}_{0}$ and mass ${M}_{0}$ ${\mathrm{cos}}^{2}$(\ensuremath{ u}t) is extended to include the effect of a driving force ${M}_{0}$${f}_{0}$ cos(\ensuremath{\lambda}t+\ensuremath{\varphi}). With \ensuremath{\varphi}\ensuremath{ e}0, catastrophic resonances occur when \ensuremath{\lambda}=(${\ensuremath{\omega}}_{0}^{2}$+${\ensuremath{ u}}^{2}$${)}^{1/2}$\ifmmode\pm\else\textpm\fi{}\ensuremath{ u}. Pseudoperiodic states exist, provided that \ensuremath{\lambda}=${\ensuremath{\omega}}_{0}$ and \ensuremath{\lambda},\ensuremath{ u} are commensurate. The corresponding quasienergies are finite in the cases \ensuremath{\varphi}=\ifmmode\pm\else\textpm\fi{}\ensuremath{\pi}/2.

Palygorskite from Tertiary Formations of Eastern Saudi Arabia

Abstract: The occurrence of palygorskite in some Tertiary sediments in eastern Saudi Arabia was studied. Mineralogical and chemical analyses were made of samples from two sections several meters thick from the Umm er Radhuma and Dammam Formations of Paleocene and Eocene periods, respectively. Layers of shales were observed within the sections of the dolomitic-calcitic limestone of the Umm er Radhuma Formation and of the dolomitic limestone of the Dammam Formation. After treatment for carbonate removal the shales consisted of more than 95% clay-size particles, most of which were <0.2-µm in size. Palygorskite was the main constituent of some of the shales, with minor amounts of gypsum, soluble salts, and carbonates. The association of gypsum and other salts with palygorskite in the shale suggests that palygorskite formed in closed-basin environments. The presence of palygorskite and the absence of other minerals in the clay fraction of the limestones also suggests that the palygorskite formed under marine conditions.

Operation of a Fixed Capacitor-Thyristor Controlled Reactor (FC-TCR) Power Factor Compensator

Abstract: A fixed capacitor-thyristor controlled reactor (FC-TCR) type of power factor compensator with thyristor-controlled series R-L load is analysed using an approximate and also a more exact circuit. The variation of power and power factor before and after compensation is examined for both cases. It is shown that considerable power factor improvement can be achieved in the circuit for low values of load thyristor firing- angle. However, for higher values of firing-angle, any improvement is obtained at the expense of additional. power losses.

Quantum well wires: electrical and optical properties

Abstract: Quantum theoretical results on electrical and optical properties of quantum well wires (QWW) are described under strong quantum confinement conditions when acoustic phonon, point defect or alloy scattering is enhanced, and ionised-impurity scattering is suppressed. A quantum size resonance is expected to take place when the energy of a photon polarised perpendicular to the wire is equal to the spacing between the quantised energy levels. The linewidth is shown to be proportional to ( lambda D2/A) tau b, where lambda D is the de Broglie wavelength of an electron. A is the confinement area, and tau b is the bulk relaxation time. A quantum freeze-out of confined carriers is expected to induce a semimetal-semiconductor transition in semimetallic thin wires.

Use of glyoxylic acid in the demonstration of autonomic nerve profiles

Abstract: 2% glyoxylic acid buffered to pH 7 could be used to improve the localization of cholinergic, adrenergic and nonspecific nerve profiles both in frozen sections and stretch preparations. The results are better than those obtained by conventional techniques, exhibiting the distinct reactions, with the least possible background and diffusion. The results are quickly obtained.

An Application of Geometric Programming to Single-Pass Turning Operations

Abstract: The solution to the problem of selecting optimum machining conditions requires sophisticated analytical techniques. The mathematical models used in the analysis of optimal machining conditions are inherently non-linear models which are constrained by the available speeds, feeds, horsepower, surface finish, etc. In this paper, a relatively new technique, the Geometric Programming is used for selecting the optimal machining conditions; cutting velocity and feed.

Effect of Temperature on the Oxygen Consumption of Lizards from different Climatic Regions

Abstract: Oxygen consumption levels and metabolic rate temperature curves of various lizard species from three different climatic regions were examined in relation to ambient temperature. The species used in this research were as follows: Anguis fragilis, Lacerta vivipara, Lacerta agilis (cool temperate species); Blanus cinereus, Podarcis hispanica, Podarcis lilfordi brauni, Podarcis lilfordi lilfordi, Podarcis muralis, Psammodromus algirus, Tarentola mauritanica (warm temperate species); Chalcides ocellatus, Acanthodactylus opheodurus, Acanthodactylus schmidti (desert species). A double chamber volumetric closed system was used to measure the resting oxygen consumption of the lizards. Acute oxygen consumption determinations were made, that is the lizards were not allowed to acclimate to the test temperatures. Interspecific differences in levels of resting oxygen consumption and in the characteristics of the metabolic rate temperature curves were examined in relation to methods of thermoregulation and in relation to the ecology of the respective species. Evidence for "temperature dependent shifts" and "low thermal dependence" was found in the metabolic rate temperature curves of some species. A diminishing Q 10 at or below the voluntary body temperatures suggests some degree of metabolic homeostatsis and energy conservation.

Transmission of Viral Infections by the Water Route: Implications for Developing Countries

Abstract: The "enteric" virus group comprises greater than 100 different viruses. These viruses typically infect the cell lining of the alimentary canal and are discharged in very large numbers in the feces of infected persons. Contamination of water supplies by enteric viruses represents an important source of viral infection. Many communities, particularly in developing countries, depend on sewage-polluted sources for their recreational and drinking water. Because conventional methods of sewage and water treatment have proved inefficient in the removal and inactivation of most enteric viruses, great concern has been raised over the impact of waterborne infection on the health of such communities. Current evidence implicating drinking and recreational water supplies in the transmission of nonbacterial gastroenteritis and hepatitis A virus and adenovirus infections is overwhelming. Water-borne transmission of other enteric viruses is also possible. Effective antiviral drugs are generally unavailable, and current vaccines can control only a limited number of viral infections; therefore, provision of uncontaminated water is a basic requirement in raising the standard of health in affected communities.

Interaction of Meloidogyne incognita and Macrophomina phaseolina in a Root‐Rot Disease Complex of French Bean

Abstract: Effects of Meloidogyne incognita and Macrophomina phaseolina on root-rot of two cultivars of French bean were examined in a greenhouse experiment. Severity of Macrophomina root-rot increased by 54.5, 94.6, and 9.6% when both pathogens were introduced simultaneously, the nematode first by 2 weeks, and the fungus first by 2 weeks, respectively. Nematode infection and reproduction was adversely affected when the fungus was introduced first. Cultivar “Harvester” was more tolerant to both pathogens and less susceptible to the nematode than “Romano Italian”. Zusammenfassung In einem Gewachshausversuch wurden die Auswirkungen von Meloidogyne incognita und Macrophomina phaseolina auf die Wurzelfaule von zwei Gartenbohnensorten untersucht. Die Schwere der Macrophomina- Wurzelfaule erhohte sich um 54,5, 94,6 und 9,6% wenn beide Pathogene gleichzeitig, der Nematode zuerst fur 2 Wochen, beziehungsweise der Pilz zuerst fur 2 Wochen, eingesetzt wurden. Die Nematodeninfektion und -reproduktion wurde gegenteilig beeinfluβt, nachdem der Pilz zuerst eingesetzt wurde. Die Sorte “Harvester” war gegenuber beiden Pathogenen toleranter und weniger anfallig gegenuber dem Nematoden als die Sorte “Romano Italian”.

Coccidia in camels (Camelus dromedarius) in Saudi Arabia.

Abstract: Saudi Arabian camels (Camelus dromedarius) are infected with three species of Eimeria: E. dromedarii (28.4%), E. rajasthani (22.2%), and E. cameli (19.2%); 41.6% of the animals examined were positive. The highest prevalence of infection was reported in the western region of the country. Mixed infection with two Eimeria species is most common; E. dromedarii was most frequently and generally the most predominant species. Eimeria dromedarii and E. rajasthani are described for the first time from Saudi Arabian camels.

Preliminary report on prevalence of oral cancer and precancerous lesions among dental patients in Saudi Arabia.

Abstract: — The study consisted of 674 consecutive examinations done on patients on their first visit the College of Dentistry, King Saud University, Riyadh, over a 1-yr period starting January 1983. Men outnumbered women and 69% ofthe patients were Saudi Arabian nationals. Oral cancer was seen in one non-Saudi, whereas the overall prevalence of leukoplakia was 1.9%. The other lesions were leukoedema 8.3%, nicotinic stomatitis 2.5%, and lichen planus 0.6%. Except for lichen planus, all the lesions were almost exclusively found in men with a close relationship to oral tobacco habits. Leukoedema, nicotinic stomatitis and leukoplakia showed a tendency to occur together in varying combinations among smokers.

A13C nuclear magnetic resonance study of some linear alkynyl gold(I) and silver(I) complexes

Abstract: Phenylacetylide gold(I) and silver(I) compounds of the type [n-Bu4N][M(C=CPh)2], (1) and [n-Bu4N][XMC=CPh], (2) have been studied by13C n.m.r. spectroscopy and their chemical shifts are reported for the first time. The shielding of the alkynyl carbon linked directly to the metal in (2) isca. 10–15 ppm less than the analogous carbon in (1) (M=Au), andca. 6–11 ppm less in the silver complexes (M=Ag). The variation in chemical shift depends on the nature of X(X=Cl, Br, I, C2Ph and Ph3P) and indicates greatly different degrees of polarization of the Au-C= (or Ag-C=) bonds in (1) and (2). I.r. spectra of the title compounds are reported and confirm the weakness of ML π back-bonding. Comparison is also made with13C and i.r. data for platinum, and mercury complexes.

An unusual presentation of histiocytosis X.

Abstract: A 20-year-old, single Saudi man was examined in the outpatient clinic in January 1980, complaining of ulcers in the groin, discharge from the right ear, and gum enlargement of 2 years' duration. Also in 1980, ulcerating lesions developed in both axillae. One year later the patient was admitted to the hospital for spontaneous pneumothorax, and in the same year a small nodule in the upper left eyelid and fissuring of the nails were noted. In 1982, the patient complained of perianal ulceration and rapidly enlarging submandibular swelling with multiple sinuses and ranula.

Recruitment control and production of market‐size Oreochromis niloticus with the predator Lates niloticus L. in the Sudan

Abstract: Experiments were conducted in earth ponds (242–1260m2) to evaluate the Nile perch (Lates niloticus L.) as a predator for recruitment control and the production of marketable Oreochromis niloticus L. in the Sudan. Supply of the predatory fish was maintained by induced spawning of L. niloticus brooders by raising the water level in a 1–0 ha earth pond. Lates niloticus fingerlings (7–5 cm total length) were then stocked with same size O. niloticus at the ratios 1:5, 1:10 and 1:15, Lates:Oreochromis, respectively. Over a period of 7 months Lates niloticus reduced young 50g) Oreochromis population and enhanced the production of preferred-size ( 200 g) Oreochromis. The ratio 1:5 Lates:Oreochromis was established to be the most desirable for Lates-with a total production of 0.2428 kg/m2 of O. niloticus with 55.7% (by weight) at the target size averaging 287.5g. The ratios 1:10 and 1:15 produced 0.2106 and 0.2153 kg m2 of O. niloticus, with 49.4% and 16.9% averaging 235.0 and 210.0 g, respectively.